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

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.

In Vitro Antimicrobial and Antiproliferative Activities of the Root Bark Extract and Isolated Chemical Constituents of Zanthoxylum paracanthum Kokwaro (Rutaceae).

Zanthoxylum paracanthum Kokwaro (Rutaceae) is an endemic Kenyan and Tanzanian plant used in folk medicine by local populations. Although other Zanthoxylum species have been studied, only Z. paracantum stem extracts have been profiled, even though the roots are also used as herbal remedies. As root extracts may be another source of pharmaceutical compounds, the CH2Cl2/MeOH (1:1) root bark extract was studied in this report. Eight root bark compounds were isolated and their structural identities were confirmed by mass spectrometry (MS) and nuclear magnetic resonance (NMR) (using COSY, HSQC, NOESY and HMBC) analyses. The structural identities were determined as follows: the fatty acid-myristic acid (1); the sterol-stigmasterol (2); the lignan-sesamin (3); two ß-carboline alkaloids-10-methoxycanthin-6-one (6) and canthin-6-one (7); and three phenanthridine alkaloids-8-acetonyldihydrochelerythrine (4), arnottianamide (5) and 8-oxochelerythrine (8). Some of these compounds were identified in the species for the first time. These compounds and the extract were then tested in vitro against methicillin-resistant Staphylococcus aureus (MRSA), Escherichia coli (ATCC 25922), Staphylococcus aureus (ATCC 29213) and Candida albicans (ATCC 10231) before tests for antiproliferative activity against the human breast cancer (HCC 1395), human prostate cancer (DU 145) and normal (Vero E6) cell lines were conducted. Minimum inhibition concentration values of 3.91, 1.95, 0.98 and 7.81 µg/mL against MRSA, S. aureus, E. coli and C. albicans, respectively, were recorded. Among the isolates, canthin-6-one was the most active, followed by 10-methoxycanthin-6-one. The root extract and some of the compounds also had antiproliferative activity against the HCC 1395 cell line. Stigmasterol and canthin-6-one had IC50 values of 7.2 and 0.42. The root bark extract also showed activity, at 8.12 µg/mL, against the HCC 1395 cells. Out of the chemical isolates, 10-methoxycanthin-6-one and canthin-6-one showed the strongest inhibition of the DU 145 cells. The root extract had significant antimicrobial and antiproliferative activities, supporting the traditional use of this plant in treating microbial infections and cancer-related ailments.

Plectranthus: a review of ethnobotanical uses.

Plectranthus is a large and widespread genus with a diversity of ethnobotanical uses. The genus is plagued with numerous nomenclatural disharmonies that make it difficult to collate accurate data on the uses. The aim of this review is to gather together all ethnobotanical information on Plectranthus and to map the data onto the most up-to-date phylogenetic classification in order to see if there are similar uses among related species and hence provide a framework for the prediction and exploration of new uses of species. The uses of 62 species of Plectranthus were mapped onto a current phylogeny based on DNA sequence data. The phylogeny reveals two major Clades, 1 and 2. The members of Clade 1 (corresponding to the formally recognized genus Coleus) were richer in number and diversity of uses than members of Clade 2 (comprising the remaining species of Plectranthus). The high incidence of synonymy can lead to problems in uncovering a species' ethnobotanical profile. About 30% of all citations of Plectranthus use a synonym and most of the synonyms are attributed to 10 of the most used species, 9 of which are in Clade 1. Members of the 'Coleus' Clade are the most studied group both taxonomically and economically. The higher incidence of study may be as a result of the higher diversity of uses and the fact that species in Clade 1, such as Plectranthus barbatus, Plectranthus amboinicus and Plectranthus mollis, are geographically more widespread than those in Clade 2. Plectranthus species in Clade 1 are frequently used as medicines and are used to treat a range of ailments, particularly digestive, skin, infective and respiratory problems. Plectranthus used as foods, flavours, fodder and materials are also mostly found in Clade 1. Monoterpenoids, sesquiterpenoids, diterpenoids and phenolics have been reported in species of Plectranthus. The abietane diterpenoids are the most diverse of the diterpenoids isolated from species of Plectranthus. The labdane diterpenoid, forskolin, occurs in Plectranthus barbatus and could explain some of the traditional uses of this species. This review highlights the fact that not enough is known about the chemistry of other species of Plectranthus to explain their traditional uses.