PHYTOCHEMICAL EVALUATION, GC-MS CHARACTERIZATION, IN VITRO ANTIMICROBIAL AND ANTIPLASMODIAL ANALYSIS

ABSTRACT

The therapeutic value of medicinal plants such as Monodora myristica, Ricinodendron heudelotii, and Piper guineense have been recognized as a component of traditional medicine for the treatment various human ailments. The therapeutic properties of a plant depend on the biochemical compounds present in the plant. This study is focused on investigating the phytochemical constituents, antimicrobial and antiplasmodial activities of n-hexane and dichloromethane extracts of these plants, as well as the characterization of the bioactive compounds in these extracts using Gas Chromatography and Mass Spectroscopy (GC-MS) methods. The dried seed samples of the medicinal plants were pulverized and extracted separately in successive extraction using n-hexane and methane. Each extract was concentrated to dryness using the rotary evaporator, to obtain their essential oils. Each of these essential oils was subjected to qualitative phytochemical analysis and further subjected to GC-MS Analysis, as well as invitro antimicrobial and antiplasmodial evaluation. In the in vitro antimicrobial activity screening done within the test concentration range of 200 - 8 µg/mL, the various plant extracts were tested against a variety of pathogenic bacteria and fungi strains, while the antiplasmodial activity of the extracts were investigated against chloroquine sensitive (D6) and chloroquine resistant (W2) strains of Plasmodium falciparum, within the test concentration range of 47.6 - 5.29 µg/mL. The phytochemical screening studied in the n-hexane and dichloromethane extracts revealed the presence of an array of phytocompounds including alkaloid, phenolics, tannins, terpenoids, saponins, flavonoids and reducing sugars. The GC-MS analysis showed the presence of 52 phytocompounds in Monodora myristica, 34 phytocompounds in Ricinodendron heudelotii and 58 phytocompounds in Piper guineense. The biochemical entities found in the seeds of the plants studied vary in their molecular weights, retention time and the amounts present. The dichloromethane extract of Piper guineense showed a potential antimalarial activity against Cryptococcus neoformans at a concentration of 53.6 µg/mL and a potent antiplasmodial activity against both strains of Plasmodium falciparum at a concentration of <5.29 µg/mL. The n-hexane extract of Piper guineense also showed a potent antiplasmodial activity at a concentration of 31.69 µg/mL and 18.44 µg/mL against the chloroquine sensitive (D6) and chloroquine resistant (W2) strains of Plasmodium falciparum. However, no antimicrobial and antiplasmodial activity was recorded on account of all the other extracts within the test concentration range of this study. These results indicate that the seeds of Piper guineense are rich in bioactive compounds which could be a potential source of new antimicrobial and antiplasmodial agents for treating diseases associated with Cryptococcus neoformans and Plasmodium falciparum.