Phytochemical screening, in vitro antimalarial activity and genetic diversity of selected asteraceae medicinal plants indigenous to Thailand

Abstract

The emergence of artemisinin resistance leaded the effort to find the new antimalarial drug or artemisinin activity booster. Due to the chance that secondary metabolites can be evolutionary conserved, combining phylogeny with ethnobotanical data for screening antimalarial activity may be helpful to predict bioactivity and minimize the expenditure and time for laboratory research. The aimed of this study is screening the antimalarial activity, phytochemicals and genetic diversity of selected Asteraceae medicinal plants generated by combinatorial phylogeny and ethnobotanical data.

733 medicinal plants were obtained from literature search however only 340 taxa were met the inclusion and exclusion criteria hence these taxa were further analysis. Obtained 340 Internal Transcribed Spacer (ITS) sequences from gene bank NCBI were analyzed by MUSCLE sequence alignment and Maximum Likelihood Phylogenetic Test to generate the phylogenetic tree. Interactive Tree of Life (ITOL) was used to analyze the clustered pattern in generated phylogenetic tree. Several clades were highlighted consistently in the phylogenetic tree for malaria treatment including Asteraceae, Apocynaceae, Rubiaceae and Euphorbiaceae while the strong signal was majorly shown in Asteraceae.

Afterwards, 16 ethanolic extract of Thai Asteraceae medicinal plants were investigated to determine the phytochemical screening, antimalarial activity, and the genetic diversity. Alkaloids, phenolics, flavonoids, triterpenes, steroids, saponins, diterpenes and lactones were screening by standard method. Antimalarial activity assay was done by DNA fluorescence-based assay against laboratory adapted 3D7 Plasmodium falciparum. Classification of antimalarial activity was done by categorizing the IC50 (µg/mL). In other hand, the genetic diversity was examined. Extracted plant DNA by CTAB method was amplified and sequenced by universal ITS primer. Phylogenetic analyses were performed with Cannabis sativa as outgroup species. MAFFT sequences alignment and RAxML with automatic bootstrapping were performed to generate phylogenetic tree followed by making up with ITOL and Adobe Illustrator 2020.

All 16 ethanolic extract medicinal plants showed the presence of phenolics and flavonoids. Among 16 medicinal plants tested, 8 showed active which exhibited good-moderate (1; Sphaeranthus indicus), weak (4; Blumea balsamifera, Artemisia chinensis, Artemisia vulgaris, Tridax procumbens) and very weak (3; Wedelia trilobata, Eupatorium capillifolium, Vernonia cinerea) and the 8 remaining extract were showed inactive. The best promising extract is Sphaeranthus indicus with the IC50 6.59 µg/mL. Constructed phylogenetic tree using ITS region showed to be able to separate the species into their clade tribe based on current classification. In conclusion, phylogeny approach is useful to narrow down the selection of candidate taxa for bioactivity screening.