Rosa californica

Rosa californica (California Wild Rose)

1. Identity: Botanical Classification, Natural Source, and Common Forms

1.1 Nomenclature and Taxonomy

Rosa californica, the California wild rose, is a species of rose native to the U.S. states of California and Oregon and the northern part of Baja California, Mexico. It is a perennial woody deciduous member of the Rosa genus in the family Rosaceae. The binomial Rosa californica was formally described by Chamisso and Schlechtendal; the meaning of its name is twofold — Rosa, that it resembles or is composed of roses, and californica, that it originates from California. The species is sometimes referred to informally as the California rose or California wild rose. The California Rose is a member of the rose family (Rosaceae), which includes herbs, shrubs, and trees with mostly prickly stems; besides garden roses and wild roses like this one, the family includes many fruit species, including apples, pears, quinces, cherries, plums, peaches, apricots, loquats, blackberries, raspberries, and strawberries.

The classification of Rosa californica within the broader Rosa genus is not without complexity. As botanist Barbara Ertter (2001) has noted, "The reason for the tremendous uncertainty in the number of species of Rosa is largely because the genus refuses to resolve itself into a tidy set of unequivocal species, under any species concept." Several synonyms and varieties have been described in the historical literature, including Rosa californica var. glandulosa Crépin and var. pubescens Crépin, though these are no longer recognized as distinct taxa under current botanical standards.

1.2 Morphology and Natural Distribution

Rosa californica is a bush or thicket-forming shrub with prickly, curving stems. The fragrant flowers may grow singly or in inflorescences of several blooms. Each rose is open-faced and generally flat, with five petals in any shade of pink from almost white to deep magenta. The five smooth petals and sepals have a bowl-like bloom, semi-inferior ovaries, and compound veiny and hairy leaves. R. californica also bears fruit called "rose hips," which contain yellow seeds.

The shrub grows 5 to 8 feet high; stems are armed with stout, flattened, usually recurved prickles with a broad base, paired at the nodes; strong shoots often bristly. Leaves are 3 to 5 inches long with a downy rachis. Leaflets are mostly five or seven, oval or ovate, usually obtuse at the apex, finely downy or glabrous above, hairy beneath, especially on the midrib and nerves, edged with simple or compound teeth.

Native distribution ranges from southern Oregon to Baja through cismontane California, and the native habitat is a variety of moist sites below 6,000 feet. While most common in moist regions like river banks, the plant can also adapt to various soil textures, develop drought resistance, and has common-pest and disease resistance. Rosa californica competes with other vegetation in moist environments because of its lateral spreading rhizomes (horizontally-spreading underground roots) and above-ground, thorny stems.

1.3 Plant Parts Used and Common Preparations

All major aboveground parts of Rosa californica have been employed ethnobotanically or as food and dietary supplement ingredients. The primary parts used are:

• Rose hips (fruit): R. californica bears fruit called "rose hips," which contain yellow seeds. They are dried for tea, or for use in jellies and sauces.
• Petals and flowers: In May through June, the blossoms could be picked and made into a beverage.
• Buds: The Cahuilla eat the rose buds raw or soaked them in water for drinking.
• Roots: The roots of this plant could also be steeped in water to make tea.
• Leaves: Used in traditional preparations combined with other plant parts (see Traditional Use section below).

Edible parts include fruit and seed; fruit may be eaten raw or cooked. Eaten raw when it becomes soft after a frost, it is much esteemed. The fruit is rich in vitamins A and C. In modern commerce, rose hips from Rosa species — including R. californica — are sold as dried whole hips, powdered supplements, standardized extracts, capsules, herbal teas, jams, syrups, and topical preparations.

---

2. Traditional and Historical Use

2.1 Indigenous California Peoples

Rosa californica has a well-documented history of use among multiple Indigenous California tribes, recorded by ethnobotanists in the twentieth century and compiled in sources such as the Native American Ethnobotany Database (BRIT). Some indigenous California tribes eat R. californica's hips raw and use the stems and fibers for crafts like coiled baskets, jewelry, and decoration. Other tribes leverage the roses' medicinal properties. They used a mix of rose petals, leaves, and/or rose "hips" in drinks or as medicine to relieve skin and general inflammation, pain, and illness (including fever, stomach pains, and sores).

Ethnobotanical records document specific uses by named tribes:

• Cahuilla: The Cahuilla used Rosa californica as a drug for analgesic purposes, as a pediatric aid, and as food (documented by Bean and Saubel, Temalpakh, 1972). The Cahuilla people were fond of eating raw wild rose hips. The hips can be crushed and turned into a jelly or else steeped in water to make tea.
• Costanoan (Ohlone): The Costanoan used Rosa californica as a drug for antirheumatic (internal), cold remedy, dermatological aid, febrifuge, gastrointestinal aid, and throat aid (documented by Bocek, 1984, Ethnobotany of Costanoan Indians).
• Kawaiisu: The Kawaiisu used the fruit of Rosa californica as a food source (Zigmond, Kawaiisu Ethnobotany, 1981). The same source also records fiber use for basketry.
• Pomo (Kashaya): The Kashaya Pomo used Rosa californica fruit as a food (Goodrich and Lawson, 1980).

Root preparations also held therapeutic value: a tea was also made from the roots and used for colds. The multipart nature of indigenous preparations — combining petals, leaves, hips, and roots — reflects a holistic approach to plant medicine characteristic of California Native traditions, and the specific records span a range of conditions from analgesic and pediatric applications to fevers, gastrointestinal complaints, skin conditions, and sore throats.

2.2 Food Use and World War II

Beyond medicine, Rosa californica hips have long served as food. The wildroses' hips are related to the Rosaceae family's apricots, apples, and roses. They are fragrant, edible, and look and taste like "small apples." The rose hips were used during World War II for their high vitamin content. These rose hips were valued during World War II on account of their high vitamin C content. Soldiers could nourish themselves while out training in the field. This use was not restricted to R. californica alone — other species such as Rosa acicularis and Rosa canina were also harvested extensively across the UK and North America during wartime food shortages when citrus imports were disrupted.

---

3. Key Constituents and Active Compounds

3.1 Overview of Phytochemistry

Rosa californica shares its core phytochemical profile with other wild Rosa species, and the genus as a whole has been extensively characterized. The genus Rosa (Rosaceae family) includes about 200 species spread in the world, and this genus shows unique advantages in medicine and food. To date, several scholars have concentrated on compounds belonging to flavonoids, triterpenes, tannins, polysaccharides, phenolic acids, fatty acids, organic acids, carotenoids, and vitamins.

Approximately 129 chemical compounds have been isolated and identified from rose hip. This fruit contains some major active components such as flavonoids, tannins, anthocyanin, phenolic compounds, fatty oil, organic acids, and inorganic compounds. In a cross-species comparative study of total phenolic content published in the peer-reviewed literature, R. californica was included alongside R. villosa, R. rugosa, R. spinosissima, and R. × damascena; the lowest total phenolic content was measured in R. × damascena (109.67 mg/100 g fresh weight), and the highest in R. rugosa (215.14 mg/100 g fresh weight).

3.2 Ascorbic Acid (Vitamin C)

Among all constituents, ascorbic acid (vitamin C) is the most intensively studied and most nutritionally significant component of rose hips. In the scientific literature, the vitamin C content in rose hips is reported to far exceed that found in citrus fruits. Rose hips are known to have the highest vitamin C content (30–1,300 mg/100 g) among fruits and vegetables. The concentration varies greatly by species and growing conditions: on the evidence of titration with 2,6-dichlorophenolindophenol, the newly ripe hips of Rosa acicularis contain 1,800 to 3,500 mg% ascorbic acid in the wet flesh; the corresponding values for R. woodsii and R. arkansana are 1,300 to 2,000 mg% or 4.0 to 6.0%. The hips of R. acicularis are the richest of the wild roses.

The fruit of Rosa californica is rich in vitamins A and C. It is important to note that processing significantly affects ascorbic acid: processing and drying of the plant destroys most of the vitamin C.

3.3 Phenolic Compounds and Flavonoids

The main phenolic compounds found in rose hips are tannins, flavonoids, phenolic acids, and anthocyanins. Rose hips are rich in some phenolic compounds, including catechin, myricetin, quercetin, procyanidin-B2, and ellagic, gallic, chlorogenic, caffeic, p-coumaric, ferulic, and sinapic acids, which significantly contribute to human health. The main phenolic components identified in rosehip pulp are procyanidin B1, chlorogenic acid, epicatechin, procyanidin B2, gallic acid, salicylic acid, and catechin.

3.4 Carotenoids and Tocopherols

Carotenoid is a dietary antioxidant, which in rosehips is represented mainly by lycopene, β-carotene, and only traces of lutein and zeaxanthin. Previous studies reported that rosehips contain higher amounts of various bioactive compounds than several other fruits, including carotenoids, vitamins (particularly vitamins C, E, and provitamin A), flavonoids, tannins, and fatty acids.

3.5 Fatty Acids and the Galactolipid GOPO

Rosa canina pseudo fruits have been used as herbal medicine for more than 2,000 years, yet research has only recently begun to clarify specific mechanisms by which this plant product affects human health. Numerous compounds have been identified, and speculations of their bioactivity have implicated flavonoids, carotenoids, and fatty acids (FAs). With more than 4,500 representatives, flavonoids have been subjected to comprehensive research, with results that suggest various individual structures may be health-promoting compounds.

Of particular mechanistic significance is the galactolipid GOPO: a specific galactolipid (1,2-di-O-α-linolenoyl-3-O-β-d-galactopyranosyl-sn-glycerol; GOPO) isolated from rose hip powder by bioassay-guided fractionation has been shown in vitro to reduce chemotaxis of peripheral blood polymorphonuclear leukocytes and monocytes. Linoleic acid and α-linolenic acid are also present, primarily in the seeds.

3.6 Minerals and Other Constituents

The dog rose hips comprise several biologically active compounds, such as sugars, organic acids, pectins, flavonoids, tannins, carotenoids, fatty acids, vitamins (particularly vitamin C and also vitamins B1, B2, K, PP, E), and macro- and microelements. Rose hips also contain minerals including potassium, calcium, phosphorus, and magnesium, as well as trace elements such as iron, zinc, and selenium.

---

4. Mechanisms of Action

4.1 Antioxidant Activity

The therapeutic potential of rosa hips is based on antioxidant effects caused by or associated with its phytochemical composition, which includes ascorbic acid, phenolic compounds, and healthy fatty acids among others. Owing to the high phenolic content, rose hips can be used as natural antioxidants. The antioxidant activity of rose hip extracts shows a good correlation with vitamin C content and total polyphenols.

4.2 Anti-inflammatory Mechanisms

Potent antioxidant radical scavenging effects are well documented for numerous rose hip constituents besides vitamin C. Furthermore, anti-inflammatory activities include the reduction of pro-inflammatory cytokines and chemokines, reduction of NF-κB signaling, inhibition of pro-inflammatory enzymes including COX-1/2, 5-LOX, and iNOS, reduction of C-reactive protein levels, reduction of chemotaxis and chemoluminescence of polymorphonuclear neutrophils (PMNs), and an inhibition of pro-inflammatory metalloproteases.

At the cellular level, rose hip powder prepared from whole dried R. canina fruits and purified GOPO attenuates inflammatory responses in cellular systems such as PMNs and chondrocytes, in a way that mirrors the reduction of the catabolic processes associated with the breakdown of cartilage in osteoarthritis or rheumatoid arthritis. Specifically, the gene expression and secretion of cytokines CCL5/RANTES, CXCL10/IP-10, IL-6, and IL-12 were reduced in LPS/interferon-activated peripheral blood leukocytes treated with rose hip powder or GOPO. Likewise, rose hip preparations reduced the expression of matrix metalloproteinase (MMP)-1, MMP-3, and MMP-13, and ADAMTS-4 in IL-1-treated normal chondrocytes.

The proposed mechanism of action has been focused on the preparations' anti-oxidative capacities, and GOPO has been identified in vitro as anti-inflammatory, and as such possibly the reason for the preparation's proposed pain-reducing property. These considerations have been confirmed by others, as extracts of R. canina fruits have shown potent anti-inflammatory and anti-nociceptive activities, and R. canina hip powder extracts may inhibit both cyclooxygenase (COX)-1 and COX-2.

4.3 Anti-proliferative and Antioxidative Effects (in vitro)

Flow cytometric analysis has revealed that Rosa canina extracts produce disturbances in the cell cycle resulting in concomitant cell death by an apoptotic pathway. Changes in the redox status of Caco-2 cells in response to rose hip hips were determined. Cells exposed to hydrogen peroxide in presence of plant fractions showed significantly decreased production of reactive oxygen species (ROS). These data demonstrate that rosehip extracts are a powerful antioxidant that produces an antiproliferative effect in Caco-2 cells. These findings are in vitro only and cannot be directly extrapolated to human cancer prevention.

---

5. Scientific Evidence by Area of Use

Important caveat: The overwhelming majority of clinical trial and mechanistic research on rose hip preparations has been conducted on Rosa canina (dog rose) and a standardized subspecies designated "Lito" — not specifically Rosa californica. Because R. californica shares closely related phytochemistry and belongs to the same genus, the scientific literature for the genus Rosa and Rosa canina in particular is the most directly relevant available evidence; this distinction is maintained throughout this section.

5.1 Osteoarthritis and Joint Pain

This is the area with the most robust and specific clinical evidence for rose hip preparations.

In vivo studies performed during the last two decades indicate that the treatment of patients with different types of joint disease with rose hip powder based on a subspecies of R. canina (Lito) containing a certain galactolipid (GOPO) can alleviate pain, improve daily activity, and even reduce the consumption of regular pain relievers.

A double-blind, randomized, placebo-controlled clinical trial with 100 osteoarthritis patients (among the 100 patients, there were 44 hip joints and 56 knee joints involved in the trial; all patients had experienced osteoarthritic pain for 2 to 12 years) found that although a significant increase was found in mobility of the hip joint and a significant decrease in pain was found in the majority of patients who received the standardized rose-hip powder, the clinical benefit of 4 months of treatment should not be overestimated. Hip joint mobility improved significantly in the treatment group compared with the placebo group (P = 0.033).

A meta-analysis published in Osteoarthritis and Cartilage reviewed randomized controlled trials comparing R. canina hip powder with placebo in patients with clinical or radiographic evidence of OA.

Subspecies Lito from Rosa canina L., Rosaceae (rose hip) has demonstrated analgesic and anti-inflammatory potential in several human trials, although results vary across studies. Differences in formulation, bioactive content, and dosing may contribute to inconsistent outcomes.

Although the number of publications of randomized and placebo-controlled clinical studies with rose hip is small, the overriding evidence is that the anti-inflammatory effects from administration of rose hip preparations containing both shells and seeds are superior to preparations containing shells alone.

Evidence strength: Preliminary to moderate. Several positive randomized controlled trials exist using standardized Rosa canina powder, but the total evidence base is small, and study populations are limited. No clinical trials specific to Rosa californica have been published.

5.2 Rheumatoid Arthritis and Inflammation

A rose-hip powder (Litozin®) has shown to reduce symptoms associated with rheumatoid inflammation in clinical trials, and extracts of this powder have shown strong anti-inflammatory activities as well as high total antioxidant capacity in vitro. Evidence from in vitro studies indicates that rose hip powder exerts anti-inflammatory properties via reduced chemotaxis of peripheral blood neutrophils and monocytes in healthy subjects, and a reduction in C-reactive protein (CRP) is seen after 4 weeks of supplementation in patients with osteoarthritis.

Evidence strength: Preliminary. There are positive signals from in vitro and animal data, and limited clinical data, primarily using Rosa canina-based preparations; no trials specific to R. californica.

5.3 Antioxidant and Vitamin C Supplementation

The therapeutic potential of these plants is based on antioxidant effects caused by or associated with their phytochemical composition, which includes ascorbic acid, phenolic compounds, and healthy fatty acids among others. The documented vitamin C content of Rosa species hips is well established chemically, and the antioxidant activity of extracts has been confirmed in multiple in vitro assay systems. However, the clinical significance of consuming rose hips specifically as a vitamin C source — as opposed to any food-based vitamin C — has not been established in controlled human trials for R. californica.

Evidence strength: Strong for the presence of ascorbic acid and antioxidant phytochemicals (established analytically); weak-to-moderate for any specific clinical benefit attributable to R. californica preparations as a vitamin C supplement beyond what would be expected from the vitamin C content alone.

5.4 Metabolic Health: Obesity and Lipid Profiles

Over the last few years, medicinal interest in rose hips has increased as a consequence of recent research that has studied their potential application as a treatment for several diseases including skin disorders, hepatotoxicity, renal disturbances, diarrhoea, inflammatory disorders, arthritis, diabetes, hyperlipidaemia, obesity, and cancer.

In a randomized double-blind, placebo-controlled clinical trial, rosehip extract decreased abdominal visceral fat in pre-obese subjects, and a powder made from the seeds and shells of rose hip species R. canina reduced symptoms of knee and hip osteoarthritis and consumption of rescue medication in patients. This study used R. canina preparations and cannot be directly attributed to R. californica. Modern pharmacological studies have also confirmed that the genus Rosa exhibits a wide range of bioactivities and nutrition, including antineoplastic and anti-cancer properties, anti-inflammatory activity, liver protection, antioxidant, regulating blood sugar, antimicrobial activity, antiviral activity, nervous system protection, and cardiovascular protection.

Evidence strength: Preliminary. Existing clinical data are for Rosa canina-specific preparations; no studies specific to R. californica have been located in peer-reviewed databases.

5.5 Antimicrobial Activity

Modern pharmacological studies have confirmed that the genus Rosa exhibits a wide range of bioactivities including antimicrobial activity. Research specifically concerning California medicinal plants has yielded relevant findings: in a study of Rhamnus californica and Umbellularia californica (not Rosa californica), researchers demonstrated in vitro antimicrobial activity against MRSA and other Gram-positive bacteria, noting that the medicinal ethnobotanical knowledge of Native Americans has been an important source for the identification of bioactive plants, and studies show a high degree of correlation between traditional medicinal uses and observed biological activity. For rose hips broadly, Rosa canina extracts were found effective in growth inhibition and biofilm formation in methicillin-resistant Staphylococcus aureus (MRSA).

Evidence strength: Preliminary; in vitro data only for Rosa species antimicrobial activity. No human clinical trials establishing efficacy for antimicrobial indications.

5.6 Gastrointestinal Health

Traditional use of Rosa californica for stomach pain and gastrointestinal ailments (particularly among the Costanoan tribe) is ethnobotanically documented. Rose hips contain pectin, organic acids, and astringent tannins. Rose hips have long been used to treat kidney stones, gastroenteric ailments, hypertension, and respiratory problems such as bronchitis, cough, and cold.

Evidence strength: Traditional use well documented; modern clinical evidence for R. californica specifically: absent.

5.7 Skin Health

Medicinal interest in rose hips has increased as a consequence of recent research studying potential application as a treatment for several diseases including skin disorders. Traditional use of Rosa californica by the Costanoan for dermatological conditions (skin sores) parallels documented modern use of rose hip oil and extracts from other Rosa species in wound healing and dermatological applications.

Evidence strength: Traditional and in vitro evidence only for R. californica; skin benefits of related species (e.g., R. canina seed oil) are better supported but involve different preparations and species.

---

6. Body Systems and Health Areas

Based on the documented traditional uses and the scientific literature for the Rosa genus, the following body systems and health areas are associated with Rosa californica preparations:

• Musculoskeletal system: Antirheumatic (internal) use is recorded among the Costanoan; the broader Rosa genus has clinical trial data for joint pain and osteoarthritis.
• Immune and inflammatory pathways: Anti-inflammatory activities include the reduction of pro-inflammatory cytokines and chemokines, reduction of NF-κB signaling, inhibition of COX-1/2, 5-LOX, and iNOS, and reduction of C-reactive protein levels.
• Gastrointestinal system: Gastrointestinal aid use is documented among the Costanoan. Rose hips contain pectin and organic acids consistent with traditional gastric use.
• Integumentary (skin) system: Indigenous use included rose petals, leaves, and/or rose hips to relieve skin and general inflammation.
• Respiratory system: Cold remedy and throat aid use is documented among the Costanoan.
• Thermoregulatory system: Febrifuge (fever-reducing) use is recorded among the Costanoan.
• Antioxidant / Metabolic: High vitamin C and polyphenol content contributes to free-radical scavenging activity relevant to oxidative stress-related conditions broadly.

---

7. Dosage Forms and Reported Dosages

No standardized dosage has been established specifically for Rosa californica preparations. Dosage information available in the scientific literature is drawn from clinical studies of Rosa canina (dog rose) preparations, and these should be understood as reference points for the genus rather than validated figures for R. californica. The following forms and doses are reported in the peer-reviewed clinical literature:

• Dried rose hip powder (standardized): The standardized rose-hip powder (SRHP) formulation designated "Lito" was used in a double-blind RCT at a specific dose for 4 months in 100 patients. Natural vitamins C and E are present in standardized rose-hip powder; however, it does not seem likely that these vitamins can explain the present findings because vitamin C was not involved in the anti-inflammatory action reported for rose-hip powder.
• Herbal tea (decoction/infusion): Hips are dried for tea or for use in jellies and sauces. Traditional preparation is variable; no standardized human trial dose has been established for R. californica tea.
• Capsules: Rose hip powder formulations using Rosa canina have been tested in standardized capsule form in clinical trials, but study-specific dosage figures are not available from the sources retrieved.
• Fresh or dried fruit (food use): Fruit may be eaten raw or cooked. Eaten raw when it becomes soft after a frost, it is much esteemed.

Importantly, most botanical products are administered at a fixed daily dose, despite significant variation in patient body weight. This results in natural variability in mg/kg exposure, offering a valuable opportunity to examine whether symptom improvement correlates with effective dose.

---

8. Safety Considerations and Drug Interactions

8.1 General Tolerability

Several years of use of rose hip powder in the Scandinavian countries has not disclosed significant data on any adverse events. The most commonly reported adverse effects are gastrointestinal: some clinical trials have reported that rose hip (R. canina) can cause loose stools, flatulence, and mild gastrointestinal discomfort.

8.2 Vitamin C Content and Related Risks

Because rose hips — including those of R. californica — contain significant quantities of vitamin C, concerns associated with high-dose vitamin C are relevant:

• Kidney stones: Large amounts of the vitamin C in rose hips might increase the risk for kidney stones. For individuals who are genetically predisposed to forming calcium oxalate kidney stones, consuming very high doses of rose hip could paradoxically increase the concentration of oxalate in the urine, potentially elevating the risk of stone formation.
• Iron absorption: Use rose hip with caution if you have iron-related disorders such as hemochromatosis, thalassemia, or anemia. The vitamin C in rose hip can increase iron absorption, which could make your condition worse.
• Sickle cell disease: It is rare, but the vitamin C in rose hip might make blood more acidic, and this could bring on a sickle cell crisis. It is best to avoid use.

8.3 Drug Interactions

Concerns about herb-drug interactions are often not based on rigorous research. Most herb-drug interactions identified in current sources are hypothetical, inferred from animal studies or cellular assays, or based on other indirect means; however, attention to this issue is needed for drugs with a narrow therapeutic index, such as cancer chemotherapeutic agents, warfarin, and digoxin.

• Warfarin (Coumadin): Rose hip contains vitamin C. Large amounts of vitamin C might decrease the effectiveness of warfarin (Coumadin). Decreasing the effectiveness of warfarin (Coumadin) might increase the risk of clotting.
• Anti-platelet / anticoagulant agents (pre-surgery): Rugosin E, a chemical found in rose hip, might slow blood clotting. There is concern that rose hip might cause bleeding if used before surgery. People taking rose hip should stop at least 2 weeks before surgery.
• Aluminum-based antacids: Rose hip has a moderate interaction rating with aluminum-containing products. Aluminum is found in most antacids. Rose hips contain vitamin C, which may enhance gastrointestinal aluminum absorption.

8.4 Special Populations

There is insufficient reliable data on the safety of medicinal doses of rose hip during pregnancy and lactation. Therefore, its use should be avoided unless approved by a healthcare provider.

8.5 Seed Hairs (Itching Powder)

The fine hairs surrounding the seeds inside rose hips are a practical safety consideration that predates modern pharmacology. These seed hairs can cause mechanical irritation of mucous membranes and the gastrointestinal tract if hips are consumed without removing or straining them. Traditional preparations such as jelly and strained tea mitigate this risk by removing the seeds and hairs before consumption.

---

9. Summary of Evidence Limitations

Rosa californica occupies an important ethnobotanical position as a historically used medicinal and food plant of California's indigenous peoples. Its phytochemical composition — high ascorbic acid, diverse polyphenols, flavonoids, carotenoids, and fatty acids — is well-established analytically and places it within the broader pattern of the Rosa genus. However, no peer-reviewed human clinical trials have been conducted using Rosa californica specifically as an intervention. All mechanistic, pharmacological, and clinical evidence is drawn from closely related species, above all Rosa canina. Although the number of publications of randomized and placebo-controlled clinical studies with rose hip is small, the overriding evidence is that the anti-inflammatory effects from administration of rose hip preparations containing both shells and seeds are superior to preparations containing shells alone. Readers and practitioners should be aware that findings from Rosa canina trials — particularly those using the proprietary standardized "Lito" powder — may not be directly transferable to preparations made from R. californica without further comparative research.

References

• Wikipedia: Rosa californica
• Jepson Herbarium, UC Berkeley: Rosa californica taxonomic page
• Lady Bird Johnson Wildflower Center: Rosa californica (California wildrose)
• Calscape / California Native Plant Society: California Wildrose
• iNaturalist: California wild rose — ethnobotanical records (NAEB database)
• Trees and Shrubs Online: Rosa californica (Bean's Trees and Shrubs)
• Plants for a Future (PFAF): Rosa californica
• The Ethnoherbalist: Wild rose hips — Native American vitamin C sources
• PMC / Journal of Ethnopharmacology (2022): Chemical constituents and pharmacological activities of medicinal plants from Rosa genus
• PMC / International Journal of Molecular Sciences (2017): Therapeutic Applications of Rose Hips from Different Rosa Species
• PMC / Plants (2023): Phenolic Compounds of Rose Hips of Some Rosa Species — Slovenia, 2020–2021
• PMC / BMC Chemistry (2013): Bioactive compounds and antioxidant activity of Rosa canina L. biotypes from Transylvania
• PMC (2020): Rose Hips, a Valuable Source of Antioxidants to Improve Gingerbread Characteristics
• PMC (2016): Rosa canina Extracts Have Antiproliferative and Antioxidant Effects on Caco-2 Human Colon Cancer
• Osteoarthritis and Cartilage (2008): Does the hip powder of Rosa canina reduce pain in OA patients? — a meta-analysis of RCTs
• NCBI Bookshelf / DARE: Does the hip powder of Rosa canina reduce pain in osteoarthritis patients (DARE review)
• PMC (2014): Effects of a Standardized Herbal Remedy from a Subtype of Rosa canina in OA — Double-Blind, Randomized, Placebo-Controlled Clinical Trial
• PubMed (2019): Rosa canina — Rose hip pharmacological ingredients and molecular mechanics counteracting osteoarthritis — A systematic review
• Dove Medical Press (2016): The role of rose hip (Rosa canina L) powder in alleviating arthritis pain and inflammation — Part II
• Botanics: Targets and Therapy (2016): Bioactive ingredients of rose hips (Rosa canina L) — antioxidative and anti-inflammatory properties, in vitro studies
• ScienceDirect / Phytotherapy Research (2011): The effects of rose hip on plasma antioxidative activity and CRP in patients with rheumatoid arthritis
• PMC (2025): Dose–Response Correlation Re-Analyzing to Distinguish Placebo from Standardized Rose-Hip Powder (Lito) in a Clinical Trial on OA
• ResearchGate / Current Pharmaceutical Design (2018): Phytochemistry, Traditional Uses and Pharmacological Profile of Rose Hip — A Review
• Canadian Journal of Research (1943): On Sources of Vitamin C: I. Rose Hips
• PMC (2018): Bioactive Compounds and Antioxidant Capacity of Rosa rugosa Depending on Degree of Ripeness
• RxList: Rose Hip — Uses, Side Effects, Interactions, Dosing, and Precautions
• NIH / NCCIH: Herb-Drug Interactions (Digest for Health Providers)
• Friends of Edgewood Natural Preserve: California Rose (Rosa californica)