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Spiroleiferthione A (<b>1</b>), with a 2-thiohydantoin a heterocyclic spiro skeleton, and oleiferthione A (<b>2</b>), an imidazole-2-thione derivative, were isolated from the aqueous extract of <i>Moringa oleifera</i> Lam. seeds. The unprecedented structures of <b>1</b> and <b>2</b> were elucidated by extensive spectroscopic data, X-ray diffraction, and gauge-independent atomic orbital (GIAO) NMR calculation, as well as electronic circular dichroism (ECD) calculation. The structures of <b>1</b> and <b>2</b> were determined to be (5<i>R</i>,7<i>R</i>,8<i>S</i>)-8-hydroxy-3-(4′-hydroxybenzyl)-7-methyl-2-thioxo-6-oxa-1, 3-diazaspiro [4.4] nonan-4-one, and 1-(4′-hydroxybenzyl)-4,5-dimethyl-1,3-dihydro-2<i>H</i>-imidazole-2-thione, respectively. Biosynthetic pathways for <b>1</b> and <b>2</b> have been proposed. Compounds <b>1</b> and <b>2</b> are considered to have originated from isothiocyanate and then undergone a series of oxidation and cyclization reactions to form <b>1</b> and <b>2</b>. Compounds <b>1</b> and <b>2</b> demonstrated weak inhibition rates of NO production, 42.81 ± 1.56% and 33.53 ± 2.34%, respectively, at a concentration of 50 μM. Additionally, Spiroleiferthione A demonstrated moderate inhibitory activity against high glucose-induced human renal mesangial cell proliferation in a dosage-dependent manner. A wider range of biological activities, and the diabetic nephropathy protective activity of Compound <b>1</b> in vivo and its mechanism of action, need further investigation after the sufficient enrichment of Compound <b>1</b> or total synthesis.