Eliciting Nature’s Activities (ELINA): a biochemometric approach to unravel complex bioactive mixtures

Although bio-guided isolation is a well-established method for the discovery of bioactive compounds from natural sources, it has many drawbacks, e.g. it is tedious, time-consuming, and not always successful. To improve this, biochemometric approaches have emerged in recent years. However, hit discovery from a complex extract containing close structural analogues remains challenging.

Hence, the aim of this work was to unravel a complex bioactive mixture of the same compound class. This was achieved by a ¹H NMR-MS workflow which we named ELINA (Eliciting Nature’s Activities) [1]. ELINA detects chemical features that are positively (‘hot’) or negatively (‘cold’) correlated with bioactivity prior to any isolation. The approach is exemplified in the discovery of steroid sulfatase (STS) [2] inhibiting lanostane triterpenes (LTTs) from the polypore fungus Fomitopsis pinicola Karst.

To reduce the complexity of the extract, a single fractionation step was performed to give 32 fractions. This was done in a way to achieve varying concentrations of a constituent over several fractions. Aliquots of all fractions were forwarded to ¹H NMR, LC-HRESIMS, and bioactivity testing. Using statistical heterocovariance analysis (HetCA) [3], ¹H NMR spectra were correlated with bioactivity data and complemented with MS data.

The effectiveness of this approach was demonstrated by disclosing chemical features crucial for STS inhibition, thus taking advantage from the innate compound library produced by the polypore’s biosynthetic machinery. As a proof of concept piptolinic acid D and pinicolic acid B equipped with these imperative features were isolated and showed IC₅₀s of 10.5 µM and 12.4 µM, respectively [1].

Fig. 1

• References

• 1 Grienke U, Foster PA, Zwirchmayr J. et al. ¹H NMR-MS-based heterocovariance as a drug discovery tool for fishing bioactive compounds out of a complex mixture of structural analogues. Sci Rep 2019. doi: DOI:10.1038/s41598-019-47434-8.
• 2 Mueller JW, Gilligan LC, Idkowiak J. et al. The regulation of steroid action by sulfation and desulfation. Endocr Rev 2015; 36: 526-563.
• 3 Aligiannis N, Halabalaki M, Chaita E. et al. Heterocovariance based metabolomics as a powerful tool accelerating bioactive natural product identification. ChemistrySelect 2016; 1: 2531-2535.