Two populations of Physalis patula Miller collected in different localities (Querétaro and Teotihuacán) of Central México were analyzed. Eight new compounds including three withanolides, physapatolides A-C (1-3), two labdanes, 12-epi-physacoztomatin (10) and physapatulone (12), besides three 12-O-glucosyl labdanes, patulosides A-C (13-15), were isolated from these collections. A series of known withanolides, flavonoids, labdanes, sucrose esters, and sterols were also isolated. Withanolides isolated of each population exhibited different substitution patterns of ring D, thus while 15,16-dioxygenated withanolides were found in the Querétaro population, oxygenation occurs at C-14 and C-15 in those isolated from Teotihuacán population. The structures of all the isolated compounds were determined by analysis of their spectroscopic and spectrometric data. The absolute configuration assigned to physapatolide A (1) was confirmed by X-ray diffraction analysis of its acetyl derivative 1a, while those of labdane diterpenoids were based on chemical correlations. The antibacterial activity of 16 of the isolated compounds (1-3, 5-9, 13, 14, and 16-21) and two derivatives (13a, 14a) was evaluated against five ATCC bacterial strains (Escherichia coli, Klebsiella pneumoniae, Pseudomonas aeruginosa, Staphylococcus aureus and Bacillus subtilis). Compounds 1-3 inhibited around 100 % the growth of S. aureus at 250 μg/mL (w/v). The minimum inhibitory concentrations (MIC) of compounds 1, 2, and 3, against S. aureus were 62.5, 125 and 62.5 μg/mL, respectively, whereas their MIC's against a Methicillin-resistant S. aureus (MRSA) clinical isolate were 125, 62.5 and 62.5 μg/mL, respectively.
Keywords: Antibacterial activity; Flavonoids; Labdane glucosides; Labdanes; Physalis patula; Solanaceae; Sterols; Sucrose esters; Withanolides.
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