Estudo fitoquímico de espécies do gênero Urochloa (Poaceae) e contribuição ao estudo de Cespedesia spathulata (Ochnaceae)

Abstract

The chromatographic techniques applied to Urochloa ruziziensis extracts and partitions, together with the application of physical methods of organic analysis, allowed the isolation and identification of eight substances, among them the organic acids already known in the genus, one flavonoid, tricin, and two steroidal saponins, dioscin and collettinside III, and the triterpene saponins 3-O-β-D-glycopyranosyl sitosterol and 3-O-β-D-glycopyranosyl stigmasterol. In addition to the classical phytochemical study, the crude extracts of U. ruziziensis and U. humidicola were analyzed by dereplication using UPLC-MS. Their profiles were compared, being common the presence of diosgenin and penogenin skeleton saponins, together the sugar type unities rhamnose and glucose. In the species U. ruziziensis it was possible to identify seven more substances, among them four flavonoids, carlinoside, schaftoside, isoschaftoside and ombuin 3-O-rutinoside. The saponin dioscin and / or collettinside III, that were also identified during chromatographic isolation and protodioscin and penogenin 3β- O- β-D-glucopyranosyl-[(2-1)-O-α-L-rhamnopyranosyl-(4- 1)-O-α-L-rhamnopyranosyl. In U. humidicola it was possible to identify, through dereplication, five substances. Tricetin derived flavonoid, tricetin 7-methyl-ether-3’-O-β-D-glucosyl-5’-O-α-L-rhamnoside and the suggestion of unprecedented tricetin 4’-O-β-D-glucosyl-[(2-1)-α-rhamnosyl-(4-1)-α-L-rhamnopyranosil]. The saponins Pariphyllin A, Solanigroside H and 3-O-β-D-glucopyranosyl-(1-4)-α-L-rhamnopyranosyl-(1-4)-β-D-glucopyranosyl-(1-4)-[α-L-rhamnopyranosyl- (1-2)]-β-D-glucopyranosyl spirost-5-eno. Specific differences were noticed mainly in the flavonoid types presente in both, since in relation to the metabolite classes we expected the identification of steroidal saponins and flavonoids. The contribution to the phytochemical study with the species Cespedesia spathulata, allowed expanding the knowledge regarding the phytochemical composition of the species. In addition to the ochnaflavone biflavonoid already identified, chromatographic processes and physical analysis methods allowed to the identification of additional twenty-six substances. The flavones vitexin, orientin and 6’’-acetyl-vitexin, two flavan-3-ols catechin e epicatechin, two steroids sitosterol and stigmasterol, the alcohol phytol, (Z)-hexadec-7-enal, hexadecyl (4-methylpentyl) oxalate, 5-heptyldihydro-2(3H)-furanone, 2-(5-oxohexyl)cyclopentanone, 1,10-bis(2-ethylhexyl)decanediate and thirteen aliphatic methyl esters. The ethyl acetate partition, derived from the raw leaf extract of this species, and the ochnaflavone, catechin and epicatechin mixture, isolated from the same partition, had their enzymatic influencing potential tested against the action of the tyrosinase enzyme. Only the partition and catechins showed activation on the action of the tyrosinase enzyme, 104% and 384%, respectively.