Identification of antifungal bisphosphocholines from medicinal Gentiana species

Authors: REN, SIYU - University Of Mississippi; DENG, KEJUN - University Of Mississippi; QIU, SHI - University Of Mississippi; Wang, Mei; AVULA, BHARATHI - University Of Mississippi; TRIPATHI, SIDDHARTH - University Of Mississippi; JACOB, MELISSA - University Of Mississippi; GONG, LIMIN - Hunan University Of Chinese Medicine; WANG, WEI - Hunan University Of Chinese Medicine; KHAN, IKHLAS - University Of Mississippi; LI, XING-CONG - University Of Mississippi

Submitted to: Journal of Natural Products
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/25/2020
Publication Date: 10/14/2020
Citation: Ren, S., Deng, K., Qiu, S., Wang, M., Avula, B., Tripathi, S.K., Jacob, M.R., Gong, L., Wang, W., Khan, I.A., Li, X. 2020. Identification of antifungal Bisphosphocholines from medicinal Gentiana species. Journal of Natural Products. 2020, 83, 10, 3207–3211. https://doi.org/10.1021/acs.jnatprod.0c00584.
DOI: https://doi.org/10.1021/acs.jnatprod.0c00584

Interpretive Summary: In our search for antifungal compounds from natural sources, the ethanol extract of the roots of Gentiana crassicaulis showed potent in vitro antifungal activities against the clinically important fungal pathogens Crypococcus neoformans and Aspergillus fumigatus. C. neoformans is the causal agent of cryptococcosis resulting in 20-70% mortality rate in immunocompromised patients, while A. fumigatus infects both immunocompromised and immunocompetent individuals leading to invasive aspergillosis with a high mortality rate up to 95%. Given the fact that our previous antifungal screening of plant extracts generated an extremely low hit rate against A. fumigatus, this extract appeared to be a good subject for follow-up bioassay-guided fractionation. In this study, the bisphosphocholine compound irlbacholine was identified as the primary constituent of G. crassicaulis responsible for the observed antifungal activity, along with three new irlbacholine analogues, gentianalines A, B and C. In addition, 56 Gentiana samples (45 from G. crassicaulis, 3 from G. dahurica, 5 from G. macrophylla, and 3 from G. straminea) that are used in traditional Chinese medicine as ‘Qinjiao’ for the treatment of rheumatism, hepatitis and pain were analyzed, indicating the bisphosphocholines are ubiquitous antifungal constituents in these plants. Identification of the bisphosphocholines, a rare class of antifungal natural products, in these medicinal plants provides scientific evidence to complement their medicinal use.

Technical Abstract: Gentiana species including G. crassicaulis, G. macrophylla, G. dahurica, and G. straminea are used in traditional Chinese medicine (TCM) as ‘Qinjiao’ for the treatment of rheumatism, hepatitis and pain. Antifungal bisphosphocholines (irlbacholine and three new analogues, gentianalines A-C) were identified from G. crassicaulis by a bioassay-guided fractionation and structure elucidation approach. Subsequent chemical analysis of 56 Qinjiao samples (45 from G. crassicaulis, 5 from G. macrophylla, 3 from G. dahurica, and 3 from G. straminea) showed that bisphosphocholines were ubiquitously present in the four Gentiana species, with irlbacholine as the major compound ranging from 2.0-6.2 mg per gram dried material. Irlbacholine exhibited potent in vitro antifungal activity against Cryptococcus neoformans, Aspergillus fumigatus, Candida albicans, and Candida glabrata with minimum inhibitory concentrations (MICs) values of 0.63, 1.25, 10.0, and 5.0 µg/ml, respectively. Identification of the bisphosphocholines, a rare class of antifungal natural products, in these medicinal plants provides scientific evidence to complement their medicinal use.