Oil extracted from seeds of different varieties of the cultivated Sesamum indicum L and three related wild species, viz S alatum Thonn, S radiatum Schum & Thonn, and S angustifolium (Oliv) Engl, were analysed for their total unsaponifiables and for the contents and composition of the three sterol fractions (desmethyl, monomethyl and dimethyl sterols). The sterols were analysed after saponification by preparative TLC, capillary GC and GC-MS of their TMS ethers. Oils from the wild species contained more unsaponifiable material (2.3-2.4 YO) compared with the cultivated species (1.1-1.3 %). Considerable differences were observed in the total sterol contents and the relative proportions of the three sterol fractions in the oils from the four species studied. Sitosterol, campesterol, stigmasterol and A5-avenasterol were the major desmethyl sterols in all four species. The monomethyl sterol fraction consisted primarily of obtusifoliol, gramisterol, cycloeucalenol and citrostadienol. Cycloartenol and 24-methylene cycloartanol were the predominant dimethyl sterols. Variations in the composition of the three sterol fractions were observed between S indicum oils traditionally pressed by the camel-driven expellers and laboratory extracted oils from the same seeds.

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Fimbrolides from marine algae have shown promising activity against quorum sensing (QS), a chief regulatory and communication system in bacteria controlling biofilm formation and virulence factor. Nitric oxide (NO) at sublethal concentration has also been reported to induce dispersal of bacterial biofilms and increase their susceptibility toward standard biocides and antibiotics. Therefore, the combination of QS inhibitors and NO donors has the potential to control the development of biofilm and promote their dispersion via a nonbactericidal mechanism. Inspired by these ideas, novel fimbrolide-NO donor hybrid compounds were designed and synthesized. Fimbrolide-NO hybrids 6b, 6f, and 14a were found to be particularly effective as antimicrobials compared to the nonhybrid natural fimbrolides as revealed by bioluminescent P. aeruginosa QS reporter assays and biofilm inhibition assays. Significantly, these fimbrolide-NO hybrids represent the first dual-action antimicrobial agent based on the baterial QS inhibition and NO signaling.

Gram-negative bacteria such as Pseudomonas aeruginosa use N-acylated L-homoserine lactones (AHLs) as autoinducers (AIs) for quorum sensing (QS), a major regulatory and cell-to-cell communication system for social adaptation, virulence factor production, biofilm formation and antibiotic resistance. Some bacteria use indole moieties for intercellular signaling and as regulators of various bacterial phenotypes important for evading the innate host immune response and antimicrobial resistance. A range of natural and synthetic indole derivatives have been found to act as inhibitors of QS-dependent bacterial phenotypes, complementing the bactericidal ability of traditional antibiotics. In this work, various indole-based AHL mimics were designed and synthesized via the 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride (EDC·HCl) and N,N'-dicyclohexylcarbodiimide (DCC) mediated coupling reactions of a variety of substituted or unsubstituted aminoindoles with different alkanoic acids. All synthesized compounds were tested for QS inhibition using a P. aeruginosa QS reporter strain by measuring the amount of green fluorescent protein (GFP) production. Docking studies were performed to examine their potential to bind and therefore inhibit the target QS receptor protein. The most potent compounds 11a, 11d and 16a showed 44 to 65% inhibition of QS activity at 250 μM concentration, and represent promising drug leads for the further development of anti-QS antimicrobial compounds.

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