Motherwort

Proposed mechanism

Most of motherwort's measured activity belongs to the whole extract rather than to any single compound — including leonurine, which is often credited with these effects but has not been detected in European motherwort (Leonurus cardiaca) and appears specific to Chinese motherwort (L. japonicus). In isolated animal hearts and heart cells, the extract blocks L-type calcium and other cardiac ion currents, slowing heart rate and prolonging conduction, the likely basis for its traditional use in easing a racing heart. Extracts also bind the GABA-A receptor at the GABA site, which may account for the calming effect, though no isolated constituent reproduces that binding and a tested iridoid showed none. Laboratory tests show reduced platelet clumping, unconfirmed in people; anyone taking a blood thinner or antiplatelet medication should check with a clinician first. European regulators list motherwort under "traditional use" for nervous tension and nervous heart complaints such as palpitations — a category based on long-standing use and safety rather than proven efficacy, and conditioned on a doctor first ruling out serious causes. Human evidence is limited to small uncontrolled studies; no placebo-controlled trial has tested motherwort for anxiety-related palpitations.

Mechanisms describe how researchers think a compound may act, often from laboratory work — a proposed mechanism is not proof of a clinical effect in people.