On the novel action of melanolysis by a leaf extract of Aloe vera and its active ingredient aloin, potent skin depigmenting agents.

The present study was carried out to investigate the effects of an Aloe vera leaf extract, along with its standard active ingredient aloin, on the isolated tail melanophores of Bufo melanostictus tadpoles, which are a type of disguised smooth muscle cells offering excellent in vitro opportunities for studying the effects of pharmacological and pharmaceutical agents. It was found that the leaf extract of A. vera and its active ingredient aloin induced powerful, dose-dependent, physiologically significant melanin aggregating effects in the isolated tail melanophores of B. melanostictus similar to those of adrenaline per se. These preliminary findings clearly demonstrate that the extract of A. vera and its active ingredient aloin cause melanin aggregation leading to skin lightening via alpha adrenergic receptor stimulation. The present study opens new vistas for the use of A. vera regarding its clinical application as a new nontoxic melanolytic agent for the treatment of hyperpigmentation.

Effect and mechanism of action of resveratrol: a novel melanolytic compound from the peanut skin of Arachis hypogaea.

PURPOSE: The present work was carried out to determine the effects of ethanolic extracts of Arachis hypogaea and its active ingredient resveratrol on the isolated tail melanophores of the Bufo melanostictus to find the mechanism of skin lightening at the cellular level. METHODS: The tail melanophores of the tadpole B. melanostictus were assayed using the mean melanophore size index and their responses were recorded in presence of various concentrations of the plant extract and its active ingredient along with specific antagonists and potentiator. RESULTS: Significant skin lightening activity of the extract of A. hypogaea and its active ingredient resveratrol was observed on the tail melanophores of tadpole. The pigment cells responded by distinct aggregation leading to skin lightening, this effect was reversible, as re-immersion in physiological saline made the melanophores return to their normal intermediate state. These melanin aggregating effects were completely blocked by propanolol (beta blocker) and partially blocked by prazosin (alpha blocker) and were also found to be highly potentiated by reserpine. CONCLUSION: These studies suggest that the active ingredient of A. hypogaea such as resveratrol can act as a sympathomimetic compound and induce aggregation of melanophores of tadpole B. melanostictus via the induction of beta type of the adrenoceptors. The present study opens new vistas for the use of A. hypogaea and its active ingredient, resveratrol for its clinical application as a nontoxic melanolytic compound for the treatment of hyperpigmentation.

In vitro responses of fish melanophores to lyophilized extracts of Psoralea corylifolia seeds and pure psoralen.

CONTEXT: Psoralens are naturally occurring furanocumarins used in photochemotherapy of several skin diseases. They are obtained from dried ripe fruits of Psoralea corylifolia Linn. (Fabaceae). However, little research has been done to study the melanogenic activity of P. corylifolia seeds and their active ingredients on the pigment cells, the melanophores taking account of their cholinergic activity. OBJECTIVE: The present work was carried out to determine the effects of lyophilized seed extracts of P. corylifolia, along with pure psoralen on the isolated scale melanophores of Channa punctatus Bloch. (Channidae), which are a disguised type of smooth muscle cells and offer excellent in vitro opportunities for studying the effects of drugs. MATERIALS AND METHODS: Effects of lyophilized extracts of P. corylifolia and pure psoralen were studied on the isolated scale melanophores of C. punctatus as per the modified method of Bhattacharya et al. (1976) . RESULTS: The lyophilized extract of P. corylifolia and its active ingredient psoralen caused significant melanin dispersal responses leading to darkening of the fish scale melanophores, which were completely antagonized by atropine and hyoscine. These melanin dispersal effects were also found to be markedly potentiated by neostigmine, an anticholinesterase agent. DISCUSSION: In the present study, the lyophilized extract of P. corylifolia seeds and standard psoralen in different dose ranges induced powerful melanin dispersal effects of the previously adrenaline-aggregated isolated scale melanophores of C. punctatus. Comparatively, psoralen caused a more sustained and powerful melanin dispersal within the isolated fish melanophores and interestingly the concentrations required to achieve maximal dispersion of melanophore were 10 times less than that of lyophilized seed extract of P. corylifolia. The physiologically significant dose-related melanin dispersion effects of lyophilized P. corylifolia seeds and synthetic psoralen per se were found to be completely abolished by atropine and hyoscine, which are specific cholino-muscarinic receptor blockers. These data strongly indicate that in the fish C. punctatus, the dispersion of melanin granules within the scale melanophores is mediated by choline receptors of muscarinic nature. CONCLUSION: It appears that the melanin dispersal effects of the extracts of P. corylifolia and pure psoralen leading to skin darkening are mediated by cholino-muscarinic- or cholino-psoralen-like receptors having similar properties.