The continuous re-isolation of the known and non-applicable compounds are critical
problems in the discovery of biologically active compounds from natural resources
that is wasting time and resources. To efficiently solve this problem, HPLC-DAD-microfractionation
directed by disk agar diffusion assay was performed, and the active compounds were
further dereplicated using the tandem mass spectrometry-based molecular networking
[1]. Moreover, utilizing the 13C NMR spectral database to deal with the problem of diastereoisomers and precisely
determined the chemical structures from the results of dereplication among the numerous
active samples. In this case, we were able to verify the presence of all the bioactive
entities in the early research stage, no matter they are new or known compounds. The
methanolic extracts of Phoma herbarum PPM7487, Cryptosporiopsis ericae PPM7504, and Albifimbria sp. PPM945 showed significant antimicrobial activity against the Candida albicans and Cryptococcus neoformans among 150 fungal strains in a preliminary agar diffusion assay. Off-line antimicrobial
activity-based HPLC profiling of these extracts enabled a precise localization of
the active compounds in the chromatogram. The purified active compounds were dereplicated
based mainly on MS/MS database [2], and the stereoisomers were further identified
by 13C NMR spectra in comparison with the literature values. In addition to seventeen
known compounds 2–18, a new trichothecenoid analogue, namely trichoverrin C (1), was isolated and identified through this protocol. This report has demonstrated
the combination of HPLC microfractination, antimicrobial assay, and dereplication
with tandem MS assisted by 13C NMR for speeding up the antimicrobial natural products discovery process.
Fig. 1
[1] Yang JY, Sanchez LM, Rath CM, Liu X et al. J. Nat. Prod. 2013; 76: 1686 – 1699.
[2] Wang M, Carver JJ, Phelan VV, Sanchez LM et al. Nat. Biotechnol. 2016; 34: 828
– 837.
