LC-MS-Based Metabolomics for the Chemosystematics of Kenyan Dodonaea viscosa Jacq (Sapindaceae) Populations

Abstract

Dodonaea viscosa Jacq (Sapindaceae) is a medicinal plant with a worldwide distribution. The species has undergone enormous taxonomic changes which caused confusion amongst plant users. In Kenya, for example, two varieties are known to exist based on morphology, i.e., D. viscosa var. viscosa along the coast, and D. viscosa var. angustifolia in the Kenyan inland. These two taxa are recognized as distinct species in some reports. This prompted us to apply metabolomics to understand the relationship among naturally occurring populations of D. viscosa in Kenya, and to identify compounds that can assist in taxonomic delineation of the different varieties of D. viscosa from different parts of Kenya. The phytochemical variability of Kenyan D. viscosa var. angustifolia populations collected from four different geographical regions (Nanyuki, Machakos, Nairobi, and Narok) and one coastal D. viscosa var. viscosa (the Gazi) were analyzed by LC-MS using a metabolomics-driven approach. Four known compounds, two diterpenoids (dodonic acid (1), hautriwaic acid lactone (3), and two flavonoids (5,7,4′,5′-tetrahydroxy-3,6,2′-trimethoxyflavone (2) and catechin (4)) were isolated and purified from the Gazi coastal collection. The presence of these compounds and their relative abundance in other populations was determined by LC-MS analyses. Multivariate statistical analyses of LC-MS data was used for the visualization of the patterns of variation and identification of additional compounds. Eleven discriminant compounds responsible for separating chemometric clusters were tentatively identified. In an antimicrobial assay, hautriwaic acid lactone (3) and catechin (4) were the most active compounds followed by the extract from the coastal (Gazi) population. The clustering pattern of the five populations of D. viscosa suggested that the metabolite profiles were influenced by geo-environmental conditions and did not support the current classification of D. viscosa based on morphology. This study disputes the current classification of D. viscosa in Kenya and recommends revision using tools such as molecular phylogenetics.

Phytochemical Profile and Antioxidant Activities of Coleus amboinicus Lour. Cultivated in Indonesia and Poland

“…Most of the compounds putatively identified from mass spectra are based on the literature and databases. It also hinders the absolute quantitation of the detected compounds that were relatively estimated using a few external standards—one for each major phytochemical class [ 35 ]. On the other hand, most of the detected compounds are not available for procurement and are present in minor amounts, which makes the isolation cost-inefficient.…”

“…On the other hand, most of the detected compounds are not available for procurement and are present in minor amounts, which makes the isolation cost-inefficient. To overcome this, while still being able to use the data for relative comparisons between phytochemical profiles, one can use various approaches, such as fragmentation patterns [ 35 , 36 , 37 , 38 , 39 , 40 ], supported by a library search (used mainly in the present paper) or coupling (offline) to NMR spectroscopy [ 41 ]. The latter provides much more accurate structural information but is also less affordable and more laborious.…”

“…The LC–MS approach used in this study was based on the m / z -retention time pairs and normalized signals values to calculate the multivariate correlations and discrimination, an approach often used to compare plant samples within a taxon along with more advanced techniques [ 35 , 37 , 38 , 39 , 40 ], which allows compensating the lack of most phytochemical standards. Nonetheless, for absolute values, the standard-based quantification is advantageous.…”