The plant extract serves not only as a good source of bioactive compounds but also as natural pigment that can be applied as colourants in food and pharmaceutical products. The aim of this study were to determine the anthocyanin content of Garcinia mangostana peel extract (GMPE), Clitoria ternatea extract (CTE) and Syzigium cumini extract (SCE) in relation to their antioxidant activity and their colour properties. The antioxidant activities related to the phenolic constituents including anthocyanin content were determined based on the EC50 of DPPH radical scavenging activity and Ferric Reducing Antioxidant Power (FRAP) assay. The colour properties of the plant extracts were measured based on their degradation index (DI), indices of polymeric colour (PC) and colour density (CD). GMPE showed higher FRAP value and lower EC50 value which were 79.37 mmoles/g and 0.11 mg/ml, respectively, as compared to SCE extract with FRAP value, 25.66 mmoles/g and EC50 value, 0.22 mg/ml. Total monomeric anthocyanin (tmAcy) exhibited a strong correlation between FRAP assay (r2 = 0.998) and DPPH assay (r2 = 0.859). GMPE showed high CD (1.63 AU), moderate PC (0.18 AU) but low in DI (1.19 AU) while SCE exhibited low in CD (0.55 AU) and PC (0.07 AU) but moderate DI (1.26 AU). CTE exhibited high in DI (5.39 AU) and PC (0.19 AU) but moderate in CD (0.55). Hence, it can be concluded that colour pigment obtained from GMPE exhibited high antioxidant activity and better colour properties as compared to SCE and the strong correlation between tmAcy and two antioxidant activity assays which are FRAP and DPPH indicated that monomeric anthocyanin plays a major role in antioxidant activity of these plant extracts.
A new oligostilbenoid tetramer, malaysianol B (1), was isolated from the acetone extract of the stem bark of Dryobalanops lanceolata along with seven oligostilbenoids tetramers; hopeaphenol (2), stenophyllol A (3), nepalensinol B (4), vaticanol B (5) and C (6), upunaphenol D (7), and flexuosol A (8). The structures of the isolated compounds were established on the basis of their spectroscopic data evidence. The antibacterial activity of the isolated compounds was evaluated using resazurin microtitre-plate assay.
In this study, mannanoligosaccharides (MOS) were isolated from palm kernel cake by aqueous extraction using high temperature and pressure. Structural characterization of MOS was carried out using acid hydrolysis, methylation analysis, ESI-MS/MS and 1D/2D NMR. The prebiotic activity of MOS was evaluated in vitro using two probiotic Lactobacillus strains. Sugar analysis indicated the presence of mannose in each of the oligomers. Methylation and 1D/2D NMR analysis indicated that the MOS have a linear structure consisting of (1→4)-β-d-mannopyranosyl residues. ESI-MS/MS results showed that the isolated mannan oligomers, MOS-III, MOS-IV, MOS-V and MOS-VI consist of tetra-, penta-, hexa-, and hepta-saccharides with molecular weights of 689, 851, 1013 and 1151Da, respectively. Based on the in vitro growth study, MOS-III and MOS-IV was found to be effective in selectively promoting the growth of Lactobacillus reuteri C1 strain as evidenced by the optical density of the culture broth.
Four previously undescribed alkaloids, aspergillinine A-D, and four known diterpene pyrones were isolated from the potato dextrose agar (PDA) culture of Aspergillus sp. HAB10R12. The chemical structures of the isolated compounds were elucidated based on a detailed analysis of their NMR and MS data. The absolute configuration of the isolated compounds was determined by Electronic Circular Dichroism analysis coupled with computational methods. Aspergillinine A represents the first example of a diketopiperazine dipeptide containing the unnatural amino acid N-methyl kynurenine. Its absolute configuration revealed that it adopts a rather unusual conformation. Aspergillinine B represents a previously unencountered skeleton containing an isoindolinone ring. Aspergillinine C and D were similar to previously isolated diketopiperazine alkaloids, namely, lumpidin and brevianamide F, respectively. The diterpene pyrones were isolated twice previously, once from a soil-derived Aspergillus species, and once from the liquid culture of Aspergillus sp. HAB10R12. The alkaloids isolated in this study showed no antiproliferative activity when tested against HepG2 and A549 cancer cell lines.
Svalbardines A and B (1 and 2) and annularin K (3) were isolated from cultures of Poaceicola sp. E1PB, an endophyte isolated from the petals of Papaver dahlianum from Svalbard, Norway. Svalbardine A (1) is a pyrano[3,2-c]chromen-4-one, a new analogue of citromycetin. Svalbardine B (2) displays an unprecedented carbon skeleton based on a 5'-benzyl-spiro[chroman-3,7'-isochromene]-4,8'-dione core. Annularin K (3) is a hydroxylated derivative of annularin D. The structure of these new polyketides, along with those of known compounds 4-6, was established by spectrometric analysis, including extensive ESI-CID-MS n processing in the case of svalbardine B (2).
Two new diterpene pyrones, asperginols A (1) and B (2), and four known analogues (3-6) were isolated from the endophytic fungus Aspergillus sp. HAB10R12. The structures and absolute configurations of these compounds were elucidated based on the analysis of their NMR, MS, and X-ray diffraction data. The revision of the absolute configurations at C-10, C-11, and C-14 of the known diterpene pyrones (3-6) and the determination of the configuration at the polyene side chain for compounds (4-6) were made using chemical methods and vibrational circular dichroism analysis. This group of diterpene pyrone compounds showed unique structural features including a 7/6/6 tricyclic diterpene moiety with an unusual trans-syn-trans stereochemical arrangement. Compound 6 showed moderate activity against the HT-29 colon cancer cell line.