ABSTRACT
Medicinal plants such as Tetrapleura tetraptera, Aframomum sceptrum, and Justicia species have been identified to be useful in the management of several health conditions, such as malaria, microbial infections, and inflammation. This study aims to determine the phytochemical constituents, antimicrobial and antiplasmodial activities of n-hexane and dichloromethane extracts of the plants under investigation. Phytochemical Screening of the extracts (aqueous, n-hexane and dichloromethane) was carried out to identify the presence of alkaloids, saponins, reducing sugar, tannins phenolics, flavonoids and terpenoids in the studied plant species. The oily n-hexane extract was characterized using GC-MS analysis. The plant extracts were also investigated for their antimicrobial and antiplasmodial activities using in vitro methods. The result obtained from the phytochemical screening of T. tetraptera showed that the aqueous extract contained alkaloids, reducing sugar, saponins, tannins, phenolics, flavonoids except terpenoids. However, the n- hexane extract of T. tetraptera showed the presence of terpenoids while the dichloromethane extract of T. tetraptera showed the presence of saponins, phenolics, tannins, and flavonoids. From the result obtained from A. sceptrum, alkaloids were discovered in aqueous and dichloromethane extract but absent in n-Hexane extract. Reducing sugar was absent in all the extracts. Alkaloids, saponins, phenolics, tannins and flavonoids were absent in n-Hexane extract but present in aqueous and dichloromethane extracts. Terpenoids were absent in aqueous and dichloromethane extracts but present in nHexane extract. The aqueous and methanolic extracts of Justicia species contained alkaloids, saponins, phenolics and flavonoids while dichloromethane extract showed the presence of alkaloids, saponins and flavonoids, GC-MS characterization of the investigated plant species revealed the presence of several bioactive compounds contained in the plant species in various percentages, and these may be responsible for the effects observed in the plant species. The n-Hexane and dichloromethane extracts of T. tetraptera, A. sceptrum and Justicia species showed significant inhibition of Plasmodium falciparum in the primary screening. These were further subjected to secondary antiplasmodial screening against Chloroquine-sensitive (D6) and Chloroquine-resistant (W2) P. falciparum strains with IC50 values of (12.89, 6.21µg/ mL) and (5.99, <5.2µg/mL) for n-Hexane and dichloromethane extracts of Aframomum sceptrum, respectively. n- Hexane and Dichloromethane extracts of T. tetraptera showed x significant inhibition of chloroquine-sensitive (D6) and chloroquine-resistance (W2) at IC50 values of (17.22, 6.19µg/mL) and (7.70,7.65µg/mL), respectively. The dichloromethane extracts of Justicia species showed moderate inhibition against D6 (Chloroquine-sensitive) strain of P. falciparum at IC50 value of 11.92ug/mL but highly significant against the W2 (chloroquine-resistant) strain at 0.091µg/mL. The result of the experiment showed that the extracts of the investigated plant species possess significant antiplasmodial activities. The dichloromethane extract of Aframomum sceptrum also showed significant inhibition of Cryptococcus neoformans, Methicillin-resistant Staphylococcus aureus and Vancomycinresistant enterococcus at IC50 values of 43.9µg/mL, 192.9µg/mL and 98.3µg/mL, respectively. It can be concluded that the crude extracts of the different medicinal species possess antimicrobial and antiplasmodial activities.
