LC-MS based metabolite profiling reveals hydroxylcinnamoyl conjugation as a discriminatory chemical factor between two closely related Coccinia species

The fruits of Coccinia grandis (L.) Voigt have been used to treat several aliments in traditional medicine whereas Coccinia rehmannii Cogn. fruits are consumed as food due to their high starch content. Coccinia rehmannii are also known to contain vast amounts of indispensable bioactive compounds that are used in various cosmetics, foods, and medicines. Among these compounds are hydroxycinnamic acids (HCAs) which are usually conjugated/esterified to quinic acid (QA), tartaric acid, citric acid, shikimic acid and sugars and are collectively referred to as chlorogenic acids (CGAs). Over the years, metabolite profiling has been used in plant taxonomy and species classification. Herein, UPLC-qTOF-MS/MS semi-targeted approached was use to profile HCA conjugates from two closely related plant species i.e. C. grandis and C. rehmannii leaves in order to distinguish them from each other. Examination of their relative metabolite contents showed that the two closely related Coccinia species utilise contrasting means of HCA conjugations as means of metabolite diversification strategy. C. grandis was found to conjugate its HCA derivatives to a QA, whilst C. rehmannii conjugates its HCA derivatives to mainly flavonoid glycosides and to QA, even though present in low concentration in this plant. These results shows that plants from the same genus can utilise different chemical diversification means for storage of their metabolites and that processes such as conjugation and isomerization can be exploited as chemotaxonomic markers. Future studies can also be designed to look at the pharmacological potency of these plants as a function of their contrasting chemical differences.