Diosgenin is a spiroketal steroidal natural product extracted from plants and used as the single most important precursor for the world steroid hormone industry. The sporadic occurrences of diosgenin in distantly related plants imply possible independent biosynthetic origins. The characteristic 5,6-spiroketal moiety in diosgenin is reminiscent of the spiroketal moiety present in anthelmintic avermectins isolated from actinomycete bacteria. How plants gained the ability to biosynthesize spiroketal natural products is unknown. Here, we report the diosgenin-biosynthetic pathways in himalayan paris ( Paris polyphylla ), a monocot medicinal plant with hemostatic and antibacterial properties, and fenugreek ( Trigonella foenum–graecum ), an eudicot culinary herb plant commonly used as a galactagogue. Both plants have independently recruited pairs of cytochromes P450 that catalyze oxidative 5,6-spiroketalization of cholesterol to produce diosgenin, with evolutionary progenitors traced to conserved phytohormone metabolism. This study paves the way for engineering the production of diosgenin and derived analogs in heterologous hosts.

A novel yellow-pigmented, non-motile, non-sporulating, catalase- and oxidase-positive, obligately aerobic, moderately halophilic, facultatively alkaliphilic Gram-positive coccus, strain YIM Y15T, was isolated from a brine sample from a salt mine in Yunnan, south-west China. Strain YIM Y15T grew in the presence of 0.5–25 % (w/v) NaCl and at pH 6.0–10.0, with optimum growth at 8–10 % (w/v) NaCl and pH 8.0. It grew at 4–45 °C, with optimum growth at 37.0 °C. The major cellular fatty acids were anteiso-C15 : 0 and iso-C15 : 0. Menaquinone 6 (MK-6) was the major respiratory quinone. The cell wall contained Lys and Gly. The DNA G+C content was 46.2 mol%. Phylogenetic analyses based on 16S rRNA gene sequence comparisons revealed that strain YIM Y15T was a member of the genus Salinicoccus, with low 16S rRNA gene sequence similarity to the type strains of the five described species of the genus, Salinicoccus alkaliphilus JCM 11311T (sequence similarity 96.0 %), Salinicoccus roseus DSM 5351T (94.9 %), Salinicoccus jeotgali KCTC 13030T (94.8 %), Salinicoccus salsiraiae LMG 22840T (94.8 %) and Salinicoccus hispanicus DSM 5352T (94.7 %). Together with the phenotypic differences, these results supported the proposal of a novel species of the genus Salinicoccus, Salinicoccus kunmingensis sp. nov., with YIM Y15T (=DSM 17847T =CGMCC 1.6302T) as the type strain.

An unprecedented new natural product named nocarsin A (1), 5H-4a,6,7a-triazacyclopenta[cd]indene-5,7(6H)-dione (1), together with seven known compounds lumichrome (2), cyclo (L-Leu-L-Tyr) (3), cyclo (L-Ala-L-Ile) (4), cyclo (L-Ala-L-Leu) (5), cyclo (L-Val-L-Ala) (6), 5-methyluracil (7) and uracil (8), was isolated from Nocardia alba sp.nov (YIM 30243(T)), which was isolated from a soil sample collected from Yunnan Province, P. R. China. NMR techniques including COSY, HSQC, ROESY, and HMBC were used to elucidate the structures of these compounds. We report the unambiguous assignments of the (1)H and (13)C NMR spectra of the new compound nocarsin A (1).

Gilvocarcin-type polyketide glycosides represent some of the most powerful antitumor therapeutics. Bioactivity-guided fractionation of a culture extract of Streptomyces polyformus sp. nov. (YIM 33176) yielded the known gilvocarcin V (2) and a novel related compound, polycarcin V (1). Structure elucidation by NMR and chemical derivatization revealed that the congener (1) features a C-glycosidically linked alpha-L-rhamnopyranosyl moiety in lieu of the D-fucofuranose. The concomitant production of two distinct furanosyl and pyranosyl C-glycosides that share the same aglycone is unprecedented in bacteria. A conversion of both isoforms via a quinone methide intermediate can be ruled out, thus pointing to two individual C-glycosylation pathways. Cytotoxicity profiling of polycarcin V in a panel of 37 tumor cell lines indicated significant antitumoral activity with a pronounced selectivity for non-small-cell lung cancer, breast cancer and melanoma cells. As the antiproliferative fingerprint is identical to that of actinomycin D, the known DNA interaction of gilvocarcins was established as a general principle of antitumorigenic activity.

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