Discovering COX-Inhibiting Constituents ofMorusRoot Bark: Activity-Guided versus Computer-Aided Methods

Abstract

The aim of this study was to compare the efficiency of two well known approaches for the discovery of the bioactive principle/s in medicinal plants, namely the activity-guided isolation versus the computer-aided drug discovery by means of virtual screening (VS) techniques. Morus root bark of Morus sp. L. (Moraceae) was selected as application example for the discovery of compounds with anti-inflammatory activity. The two cyclooxygenase isoenzymes COX-1 and COX-2 were chosen as targets and the corresponding pharmacophore models were generated by our research. The activity-guided fractionation of the methanol extract of the root bark resulted in the isolation of nine compounds. Their structures were elucidated by mass spectrometry, 1- and 2-dimensional NMR experiments and identified as moracins B, M, the regioisomers O/P as a mixture, and sanggenons B, C, D, E and O. The COX-1 and COX-2 inhibiting activities of these compounds were established in an enzyme assay and compared with the predicted hits obtained from the VS. Sanggenons C, E, and O, that were tested the first time for an inhibitory effect on COX-1 and -2, showed IC50 values of 10-14 microM, and 40-50 microM, respectively. The results show that the COX activities obtained for the sanggenons are correctly predicted by the in silico filtering experiment. In the case of the isolated moracins, however, it failed because the COX inhibiting activities of moracins M and P/O were not retrieved by the VS. Structure-activity relationships of the isolated compounds are discussed as well as potential pitfalls and advantages of the applied strategies.

Discovering anti-osteoporosis constituents of maca (Lepidium meyenii) by combined virtual screening and activity verification

“…However, virtual screening is based on existing knowledge of chemical plant constituents and pharmacophore models, and thus cannot fully reflect organismic complexity. By previous methods, it was difficult to avoid missing valuable compounds (Rollinger et al, 2005). Although we found that Nbenzyl-palmitamide is an active constituent of maca in osteoporosis prevention, this fact does not deny the role of other components.…”

Pharmacophore Models for Virtual Screening

“…This shows that natural products have a great potential as COX inhibitors. Thus, Rollinger et al [139] used a pharmacophorebased workflow for identifying novel ligands. They virtually screened the DIOS database and retrieved several compounds originating from the genus Morus.…”

“…This resulted in the discovery of moderate COX inhibitors. For example, sanggenon E (1, Figure 5.11) gave an IC 50 value of 10.8 mM for COX-1 inhibition [139].…”

Predicting Cyclooxygenase Inhibition by Three‐Dimensional Pharmacophoric Profiling. Part I: Model Generation, Validation and Applicability in Ethnopharmacology

“…[17][18][19][20] The availability of X-ray crystal structures with bound inhibitors, a large number of known active ligands, and the availability of datasets for theoretical model validation, i.e. subsets from the directory of useful decoys (DUD) database, [21] made COX-1 and -2 an ideal case study.…”

“…In contrast, we deliberately include COX-1 inhibitors into this study. We aim at developing a tool for elucidating the mode-of-action of ethnopharmacologically used natural products, of which many are already known COX-1 inhibitors, e.g., [16,17,[28][29][30]. Neglecting this important anti-inflammatory mechanism would hinder the identification of anti-inflammatory compounds.…”