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Herba Leonuri
demonstrated that in addition to elevating endogenous antioxidant enzyme
activity, Herba Leonuri, used traditionally in Chinese herbal
medicine for the treatment of cardiovascular disorders, contains a potent
antioxidant component capable of effective inhibition of oxidative
reactions mediated by the inflammatory oxidants, peroxynitrite, hypochlorous
acid and hydroxyl radicals, as well as iron-dependent lipid
peroxidation (49).
The antioxidant and cardioprotective effects of an extract of Herba
Leonuri on ischaemic myocardium were investigated in rats. A daily
dose of the extract (400 mg/kg bw per day) was administered orally
starting from 1 week before and continuing until 3 weeks after myocardial
infarction. Surviving rats were killed at different times to obtain left
ventricles for biochemical assays. The results demonstrated for the first
time that Herba Leonuri has antioxidant effects both in vitro and in
vivo. The antioxidant effects of the extract are exerted only under the
condition of oxidative stress, by selectively preserving the activities of
superoxide dismutase and glutathione peroxidase, as well as depressing
the formation of malondialdehyde. Its effects of scavenging free radicals
and inhibiting the formation of reactive oxygen species probably play a
role in protecting the endogenous antioxidant system from oxidative
stress in vivo (50).
Antitumour activity
Herba Leonuri demonstrated cytotoxicity during in vitro studies on lymphocytic
leukaemia (P-388, L-1210), KB cells, human lung carcinoma (A-
549), mammary tumour (MCF-7) and human colon tumour cells (HCT-
8) (51). Ingestion of the methanol extract of Herba Leonuri in
drinking-water at a concentration of 0.5% markedly suppressed the development
of mammary cancers in multiparous GR/A mice. The incidence
of uterine adenomyosis was also inhibited in mice given an extract
of Herba Leonuri. The stimulation by the extract of the excretion of any
carcinogenic factors may at least partly contribute to its inhibition of
mammary cancers (52).
Toxicology
No documented toxicity studies were found, but ursolic acid has been
reported to have cytotoxic activity (51). A median lethal dose for the
extract of Herba Leonuri in rats of 10.8 g/kg bw by intraperitoneal
injection has been recorded (47). In the USA, Herba Leonuri is listed
by the US Food and Drug Administration as a “herb of undefined
safety” (53).
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