MOLECULAR PHYLOGENY, PHYTOCHEMICAL COMPOSITION AND BIOLOGICAL ACTIVITIES OF SELECTED KENYAN POPULATIONS OF DODONAEA VISCOSA (SAPINDACEAE)

Abstract

The family Sapindaceae is diverse, with four subfamilies. The genus Dodonaea (Sapindaceae) is endemic to Australia and widespread in Kenya in various habitats. There are two varieties found in Kenya. The taxonomic relationship between them is quite confusing. The two have many ethnomedicinal uses. Microbial organisms cause several diseases in plants and animals and with time, have developed resistance to most conventional drugs. The phytochemical components of plants haave specific pharmacological effects on the human body and exert their therapeutic value. Secondary metabolites isolated from plants are also important in chemotaxonomy. This study provided a phylogenetic analysis that included nucleotide frequency and substitution rates, base composition disparity index and evolutionary divergence. Eleven Kenyan populations of Dodonaea viscosa had their ribulose-bisphosphate carboxylase (rbcL) and internally transcribed spacer 1 (ITS1) genes extracted and Sanger sequenced. They were aligned by MUSCLE (codons) and exported to MEGA 11 and PhyloSuite for analysis. Phylogeny was constructed using ML and ITOL used to edit the cladograms. Prior to phylogenetic analysis a nucleotide BLAST of the sequence genes was done to identify the closest ancestor of Dodonaea viscosa. The sequences were also subjected to analysis by PCA. An analysis of phytochemical constituents of DCM: CH3OH leaf extract was conducted on Gazi 1C population. The agar well diffusion method was used to determine the antimicrobial activity, while antidiabetic activity was carried out on Swiss albino rats. Data on antidiabetic activity were organized in excel tables and analyzed using ANOVA, and paired sample t-test. Graphical method was used to analyze data on antimicrobial activity. From the phylogenetic analyses, a narrow genetic distance exists amongst the Kenyan populations of Dodonaea viscosa. The PCA showed more variations in the Dodonaea populations studied using the rbcL gene compared to using the ITS1 gene. Phytochemical analysis identified 4 compounds from the leaves, which supplemented the bulk of data for chemotaxonomic analysis. This study revealed that the crude extract of Dodonaea viscosa was antidiabetic as it lowered blood sugar in STZ induced diabetic rats. Likewise, the crude extract showed antibacterial and antifungal activities, as evidenced by the inhibition zones, except in Escherichia coli. The antidiabetic activity of the roots and leaves of various populations did not differ significantly, at P-value of >0.05. Variance between the populations was also not statistically different, as the P-value was 0.742. More antidiabetic activity was observed in the reference drug, followed by the plant extract at a dose of 400 mg/kg bwt, with the lowest activity at 200 mg/kg bwt. Similarly, more antimicrobial activity was observed from the positive controls (Amoxicillin and Apron), followed by the plant extracts. More studies targeting other gene areas with different primers are recommended to establish a full relationship between the Dodonaea viscosa Kenyan populations. There is a need for more bioassays on the compounds isolated from this study to determine the biological potential of this widely distributed plant.