Triterpenoid saponins from the stem bark of Caryocar villosum
Résumé
Five triterpenoid saponins, caryocarosides II-22 (3), III-22 (4), II-23 (5), III-23 (6), and II-24 (7), have been isolated from the methanol extract of the stem bark of Caryocar villosum, along with two known saponins (1–2). The seven saponins are glucuronides of hederagenin (II) or bayogenin (III). Caryocaroside II-24 (7) is an unusual galloyl ester saponin acylated on the sugar chain attached to C-28, the 3-O-α-l-rhamnopyranosyl-(1 → 3)-β-d-galactopyranosyl-(1 → 3)-β-d-glucuronopyranosyl hederagenin-28-O-[2-O-galloyl-β-d-glucopyranosyl] ester. The structures of the saponins were established on the basis of extensive NMR (13C, 1H, COSY, TOCSY, HSQC, HMBC and ROESY) and ESI-MS studies. The cytotoxic activity of saponins 2 and 3 was evaluated in vitro against human keratinocytes. The DOPA-oxidase inhibition and the lipolytic activities were evaluated ex vivo using an explant of human adipose tissue.
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