Astragalin, a natural flavonoid (kaempferol-3-O-glucoside) found in plants such as Astragalus membranaceus and Polygonum aviculare, has been investigated for its potential vascular protective effects. Preclinical studies suggest that astragalin exhibits anti-inflammatory, antioxidant, and vasoprotective properties. These properties could theoretically benefit capillary health by reducing oxidative stress and inflammation, both of which are implicated in capillary damage and microvascular dysfunction.

For example, in vitro and animal studies have demonstrated that astragalin can attenuate endothelial cell apoptosis, reduce reactive oxygen species (ROS) production, and inhibit the expression of inflammatory mediators such as TNF-α and IL-6. Some research also suggests that astragalin may help maintain the integrity of the vascular endothelium and prevent increased vascular permeability, which is relevant to capillary health.

However, there is a lack of well-controlled human clinical trials directly examining astragalin's effects on capillary function or disorders specifically. Most evidence remains limited to cell culture or animal models, and the translation to human health is not yet established. Thus, while there is a scientific rationale and some promising preclinical evidence, clinical validation for astragalin’s use in supporting the capillaries is currently weak.