Antibacterial constituents of Rumex nepalensis spreng and its emodin derivatives.

The CH2Cl2-MeOH (1:1) extract of roots of Rumex nepalensis (Polygonaceae) displayed significant antibacterial activity against five bacterial strains with MICs (62.5-31.2 µg.mL-1). The EtOAc soluble fraction displayed a significant activity against the same strains with MICs (31.2-3.9 µg.mL-1). The purification of the EtOAc fraction yielded one new phenylisobenzofuranone derivative, berquaertiide (1), along with 19 known compounds (2-20). Their structures were elucidated based on the analysis of their NMR and MS data. All the isolated compounds were assessed for their antibacterial activity. Compound 2 was the most active against all the tested strains (15.7 to 1.9 µg.mL-1), while compounds 3-7 displayed good activities on at least one of the tested strains. In addition, seven analogues (21-27) of compound 2 were prepared and further assessed for their antibacterial activity. Compounds 26 and 27 were most active than 2 against Salmonella enterica and Klebsiella pneumoniae with MIC (125 and 15.6 µg.mL-1, respectively).

Bioactive constituents from Manilkara obovata (Sabine & G.Don) J.H.Hemsl.

The phytochemical investigation of the methanolic extracts of roots, stem bark, leaves and twigs of Manilkara obovata has led to the isolation of one new friedelane triterpene, lacefriedelic acid or 3ß,23-dihydroxy D:A-friedooleanan-28-oic acid (1) and one new prenylated xanthone, lacexanthone or 4,7-dihydroxy-2,3,3,9,9-pentamethyl-2,2-dihydrofurano[2,3-a]pyrano[2,3-i]xanthen-13(9H)-one (2) alongside twenty-four known compounds. Compounds 1-11 are reported here for the first time from the genus Manilkara. The structures of all compounds were determined by spectroscopic analyses and X-ray crystallography. The methanolic extracts of twigs and leaves showed anti-oxidant activity of 93.2 and 91.1%, respectively, at 100 µg/mL when measured by DPPH (2,2-diphenyl-1-picryl-hydrazyl-hydrate), while the twig extract displayed 86.3% at 100 µg/mL against the urease inhibition assay. Some isolated compounds (1-4, 15 and 20) showed significant to moderate anti-oxidant activity and urease inhibition assay. It is estimated that significantly active anti-oxidants and urease inhibitors metabolized by the plant may find future application in food industry.