Contribuição ao estudo químico de espécies da família Cucurbitaceae juss. e Rubiaceae juss. gêneros: Cayaponia Silva Manso e Psychotria L.
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2015-06-12
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Universidade Federal de Goiás
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This work describes the chemical evaluation and, in parallel, the investigation of
antioxidant and antimicrobial activity of four medicinal species of Brazilian
Cerrado, Cayaponia espelina (Silva Manso) Cogn., C. citrullifolia (Griseb.) Cogn.,
C. weddellii (Naudin) Gomes-Klein (Cucurbitaceae) and Psychotria trichophora
Müll. Arg. (Rubiaceae). The study of ethanol extracts of the species mentioned
above led to the isolation of several classes of secondary metabolites, many of
them presenting biological activity. Evaluation of ethyl acetate fractions of the
leaves of C. espelina and n-butanol and hydromethanol fractions of C. citrullifolia
led to the isolation and structural elucidation of seven compounds: luteolin (CE-
1), luteolin 4'-O-glucoside (CE-2), luteolin 7-O-glucoside (CE-3), kaempferol 3,7-
O-α-L-dirhamnoside (CC-1), benzyl-O-β-D-xylopyranosyl-(1→6)-β-Dglucopyranoside
(CC-4), salicylic acid 2-O-β-glucopyranoside (CC-3) and
vicenin-2 (CC-2). The glucosides CE-2 and CE-3 found in C. espelina were also
found in ethyl acetate fraction from C. weddellii leaves, indicating that there might
be a chemical similarity between these species. The fourth species investigated
in this study was P. trichophora and the chemical study of ethyl acetate fraction
of its leaves led to the isolation and structural elucidation of six compounds:
camelliaside B (PT-3), kaempferol-3-O-α-L-rhamnopyranosyl-(1→6)-[β-Dxylopyranosyl-(
1→2)]-β-D-galactopyranoside (PT-4), kaempferol-3-O-[β-Dxylopyranosyl-(
1→3)-α-L-rhamnopyranosyl-(1→6)]-β-D-galactopyranoside (PT-
5), kaempferol-3-O-robinoside (PT-2) and 3-O-p-coumaroylquinic acid (PT-6).
Coumarin scopoletin (PT-1) were identified from its roots. Structural identification
of compounds was performed by spectroscopic analysis including IR and 1H and
13C NMR, in one-and two-dimensions. Flavonoids PT-4 and PT-5, previously
isolated in the Fabaceae and Leguminosae families, were described for the first
time in Rubiaceae. Furthermore, CCDA analysis of acid-base fractions obtained
from P. trichophora leaves did not result positive for alkaloids against the
Dragendorff reagent. Preliminary tests in Escherichia coli showed that the ethyl
acetate fraction from C. espelina presents pharmacological potential, inhibiting
74 % of bacterial growth at a 82 μg/mL concentration. This fraction also exhibited
strong antioxidant activity, with IC50 value of 5.40 ± 0.16 μg/ml, being comparable
to that of the commercial antioxidant, ascorbic acid. Extracts from C. espelina
and C. weddelli were the most promising antioxidants with IC50 values of 131 ±
0.31 and 13.14 ± 0.57 μg/mL, respectively. In preliminary bioassays against
Sarcoma 180 tumor cell line, all tested samples presented low activity despite the
literature data for antitumor activity of the isolated flavonoids.
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LEMES, G. F. Contribuição ao estudo químico de espécies da família Cucurbitacea juss. e Rubiaceae juss. gêneros: Cayaponia Silva Manso e Psychotria L.. 2015. 218 f. Tese (Doutorado em Química) - Universidade Federal de Goiás, Goiânia, 2015.