Agnuside is one of the primary iridoid glycosides found in the fruit of Vitex agnus-castus (chaste tree), a botanical traditionally used for women's health, particularly for symptoms associated with premenstrual syndrome (PMS). The scientific rationale for its use in PMS is based on clinical studies and mechanistic research involving the whole extract of Vitex agnus-castus, not agnuside in isolation. Agnuside is considered a marker compound for extract standardization, and it may contribute to the observed effects, but its specific pharmacological activity is not fully established.

The most robust clinical evidence pertains to standardized Vitex agnus-castus extracts, which have been shown in several randomized controlled trials to reduce PMS symptoms, likely via modulation of prolactin and effects on dopaminergic pathways. These effects are thought to normalize menstrual cycles and alleviate symptoms such as breast tenderness, irritability, and mood swings. A 2017 systematic review concluded that Vitex agnus-castus was significantly more effective than placebo for PMS, with a good safety profile. However, the contribution of agnuside specifically—versus other active constituents such as casticin or flavonoids—is unclear.

In summary, while agnuside-containing Vitex agnus-castus extracts are scientifically validated for PMS, the evidence for agnuside alone is not well defined. Thus, the level of evidence is moderate (3/5), grounded in clinical trials of the whole extract rather than the isolated compound.