A New Ceramide (Rumexamide) and Other Chemical Constituents from <i>Rumex abyssinicus</i>Jacq (Polygonaceae): Isolation, Characterization, Antibacterial Activities and Chemophenetic Significance

The chemical study of Rumex abyssinicus Jacp (Polygonaceae) led to the isolation of a new ceramide named (R)-2'-hydroxy-N-[(2S,3S,4R,16E)-1,3,4-trihydroxyhexacos-16-en-2-yl]hexadecanamide (rumexamide) (1) together with sixteen known compounds: bis-(2-ethylhexyl) phthalate (2), chrysophanol (3), physcion (4), citreorosein (5), emodin (6), chrysophanein (7), physcionin (8), lupeol (9), 3β,28-dihydroxylup-20(29)-ene (10), 3β-dihydroxylup-20(29)-en-28-oic acid (11), oleanolic acid (12), ergosta-6,22-diene-3,5,8-triol (13), stigmastane-3,6-dione (14), a mixture of β-sitosterol (15) and stigmasterol (16), and stigmasterol 3-O-β-D-glucoside (17). Their structures were determined by interpretation of their spectroscopic 1D NMR (1H and 13C NMR), 2D NMR (COSY 1H-1H, HSQC and HMBC) data in conjunction with mass spectrometry (TOFESIMS and HR-TOFESIMS) and by comparison with those reported in the literature. Among all the known compounds, twelve (2, 5, 8-17) were firstly isolated from Rumex abyssinicus, seven (2, 10-14 and 17) from the genus Rumex and three (13, 14, 17) from family Polygonaceae. The in vitro antibacterial activities of extracts (MeOH, n-BuOH and EtOAc), as well as compounds 9, 11, 12, 15 + 16 and 17 against pathogenic bacteria (Staphylococcus aureus ATCC 43300, Shigella flexneri NR 518, Klebsiella pneumoniae ATCC 700603, Escherichia coli ATCC 25922), were performed using the broth microdilution method and the results show that, extracts were not active (MIC > 1000 μg/mL) while compounds were weakly or not active (MIC ≥ 500 μg/mL) against all bacteria strains. Furthermore, the chemophenetic relationships of the isolated compounds and their significances were discussed.

Ethnobotany, Pharmacology and Phytochemical Investigations of the Seeds of <i>Pentaclethra macrophylla</i>Benth (Mimosaceae)

Phytochemical investigation of the seeds of Pentaclethra macrophylla led to the isolation of a mixture of two new aromatic monoterpene glycosides, pentamacrophylloside A (1a) and pentamacrophylloside B (1b), together with six known secondary metabolites: Comososide (2), secopentaclethroside (3), caffeoylputrescine (4), β-sitosterol-3-O-β-D-glucopyranoside (5), 2-hydroxymethyl-5-(2-hydroxypropan-2-yl)phenol (6), and sucrose (7). Their structures were elucidated mainly by extensive spectroscopic analysis (1D and 2D NMR), high-resolution mass spectrometry and by comparison of their spectral data with those of related compounds. The extracts and compounds 3 and 4 were screened for their antimicrobial activity. The n-BuOH fraction showed a weak effect against three microbial strains: Candida albicans (MIC: 256 μg/mL), Enterococcus faecalis (MIC: 512 μg/mL), and Proteus mirabilis (MIC: 512 μg/mL) while no significant inhibition was observed for pure compounds when compared to ketoconazole and ciprofloxacin used as references. Furthermore, the ethnobotany and pharmacology of this plant are reviewed, and the chemophenetic significance of the isolation of the above secondary metabolites is discussed. This is the first report on the isolation of aromatic monoterpenoids from a plant of the genus Pentaclethra.