Saponins and secondary metabolites of the argan tree (Argania spinosa).

摘要

The secondary metabolites of the argan tree (Argania spinosa) were studied to look for identify new metabolites that might increase the tree's industrial and commercial value, thus stimulating its protection and even the extension of argan groves. Several flavonoids were isolated from its trunk: myricetin, quercetin and four of their glycosylated derivatives. The trunk of the argan tree also furnishes volatile compounds and essential oils; forty-five such derivatives have been identified. Substances isolated from the pulp of its fruit include (+)-catechin, (-)-epicatechin, rutin, p-hydroxybenzoic acid, and resorcinol. Erythrodiol, lupeol, spinasterol and betulin have also been identified. All of these secondary metabolites are common and add little value to the argan tree. More interestingly, the argan tree is rich in saponins and structures of fifteen of these compounds, from different parts of the tree, have been identified. All the saponins so far identified have a strongly hydroxylated D-12oleanane: [protobassic acid or 16a-hydroxyprotobassic derivative as the genin (aglycon) for the saponins from fruits (or fruit product preparations), and bayogenin for the wood saponins]. All the saponins are bidesmosidic with a sugar chain in positions 3 and 28 of the aglycon. These chains may be linear or branched and contain up to five osidic residues. We have also identified various biological properties of saponins isolated from the oilcake. These saponins are molluscicidal and antifungal. Leukotriene interaction induces antiinflammatory activity. Acute toxicity testing shows an LD50 of 1.3 g/kg. Chronic administration of oilcake saponins reduces blood glucose and induces renal toxicity. These saponins are also antioxidant and stimulate in vitro lipolysis. They may also protect DNA from the harmful effects of UV-B..