Natural variation in specialised metabolites production in the leafy vegetable spider plant (Gynandropsis gynandra L. (Briq.)) in Africa and Asia

Abstract

The improvement and promotion of leafy vegetables, used for both food and medicine, benefits greatly from detailed knowledge of their health-promoting specialised metabolites. In the present study, we investigated the global metabolite variation in the leaves of 48 accessions of the leafy vegetable Gynandropsis gynandra using two complementary analytical platforms: liquid-chromatography mass spectrometry (LC-MS) for an untargeted comparison of non-volatile semi-polar metabolites and gas-chromatography mass spectrometry (GC-MS) for an untargeted comparison of volatile metabolites. Our results revealed large variation in 936 semi-polar compounds

including flavonoids, terpene glycosides, glucosinolates and various phenolic compounds. Unsupervised multi- variate analysis indicated the variation in levels of the semi-polar metabolites was mainly driven by geography,

with accessions from both West Africa and Asia forming a group clearly separated from East African accessions.

Detected volatile metabolites included various sesquiterpenes, aldehydes, ketones, and sulphur-containing iso- thiocyanates. Variation in these compounds was however not geographically specific, but most likely linked to

the taste and aroma of the leaves. The relative abundance in glucosinolates and isothiocyanates in the leaves

allowed the clustering of accessions into two main groups that could be used for further plant-herbivore inter- action studies. This study revealed both the broad spectrum of phytochemicals present in Gynandropsis gynandra

leaves and the substantial variation in metabolite profiles among accessions from different regions of the world.

Our results provide a basis for the development of breeding programs aiming at improving the levels of speci- alised metabolites in this tropical leafy vegetable for increased resistance against pests and diseases and improved human health.