Comparative GC-MS analysis, In vitro antimalarial and antimicrobial evaluation of Aframomum sceptrum and Aframomum melegueta extracts

Abstract

Aframomum sceptrum (AS) and Aframomum melegueta (AM) have been used as food spices and for managing various health conditions (malaria, microbial infections, inflammation, etc.) for centuries by the people of Southern Nigeria. This study aimed to investigate the antimalarial and antimicrobial activities of the extracts as well as characterize the phytochemical constituents of the extracts by GC-MS analysis. Thus, the maceration technique was used to obtain the n-hexane and dichloromethane extracts. The extraction was characterised using GC-MS analysis. The hexane and dichloromethane (DCM) extracts were also screened for their antimalarial and antimicrobial activity using the Plasmodium lactate dehydrogenase (pLDH) assay. GC-MS characterization of the n-hexane extract of the plant species showed the presence of several bioactive compounds in various percentages, which may contribute to the plant species' bioactivity. Some of the prominent phytochemicals in different percentages from the GC-MS analysis include caryophyllene (2.23 & 5.26 %), α-Caryophyllene (2.63 & 0.31 %), Caryophyllene oxide (4.27 % 1.46 %), γ-Gurjunene (4.19 & 0.10%) and n-Hexadecanoic acid (3.86 & 3.74 &), for AS and AM, respectively. The n-Hexane and DCM extracts of AS showed significant inhibition of chloroquine-sensitive (D6) and Chloroquine-resistant (W2) P. falciparum strains with IC₅₀ values of (12.89, 6.21 µg/ mL) and (5.99, < 5.2 µg/mL) for n-Hexane and DCM extracts of AS, respectively. n-Hexane and DCM extracts of AM also showed significant inhibition of the D6 and W2 P. falciparum strains with IC₅₀ values of (29.84, 17.64 µg/mL) and (15.59, 9.16 µg/mL), respectively. The DCM extract of AS showed significant inhibition of Cryptococcus neoformans, Methicillin-resistant Staphylococcus aureus, and Vancomycin-resistant Enterococcus at IC50 values of 43.9 µg/mL, 192.9 µg/mL, and 98.3 µg/mL, respectively. The DCM extract of AM also showed significant inhibition of Cryptococcus neoformans, with an IC50 value of 60.48 µg/mL. These findings justified the various ethnomedicinal uses of these plants' seeds in treating malaria and microbial infections. They could be promising sources for the discovery of anti-infective agents.