Characterization Of Phytochemicals From Chamaecrista Nigricans Vahl And Ximenia Americana L With Antimicrobial Activities

Abstract

Infectious diseases account for most deaths globally, far beyond the damage incurred by warfare and food shortages. 10 million deaths have resulted from infectious diseases worldwide; lower respiratory tract infections are the largest, followed by diarrhoea, tuberculosis, HIV-AIDS, and Malaria. 70,000 deaths have resulted due to the increased drug resistance in malaria, antibacterial, and antifungal drugs. Bioactive compounds are continually being explored for the prophylaxis and treatment of these infectious diseases and also to manage drug resistance limitations acquired by some of the currently used drugs. This study aimed to characterize phytochemicals from the Chamaecrista nigricans plant and the Ximenia americana roots with antiplasmodial and antimicrobial activities. The grounded plant of C. nigricans and X. americana roots were extracted via cold extraction using a 1:1 methanol: DCM solvent volume ratio. Fractionation and purification were done using the silica column chromatography technique, and Sephadex LH20 was used to purify some compounds further. Chemical structures were identified using FTIR, GC-MS, and NMR spectroscopic techniques. C. nigricans yielded previously reported compounds compounds: chrysophanol (1,8-dihydroxy-3-methylanthraquinone) (SAO-04), (1,6,8-trihydroxy-3-methylanthraquinone) (SAO-05), and physcion (1,8-dihydroxy-3- methyl-6-methoxyanthraquinone) (SAO-06). X. americana yielded seven compounds: Octahydro-3-isopropyl-4a,5-dimethylnaphthalen-2 (1H)-one, Trans-2-dodecenedioic acid, Octadecanoic acid, 1,2-dihexadecanoylglycerol, Methyl-14-methylpentadecanoate, (Z)-7- tetradecenal and (Z)-9-hexadecenal. The crude extracts from the two plants had IC50 values of > 47.6 μg/ml against both P. falciparum D6 (chloroquine sensitive) and W2 (chloroquine-resistant). The compounds isolated from the two plants exhibited antiplasmodial activity with IC50 values of > 4.76 μg/ml against both P. falciparum D6 (chloroquine sensitive) and W2 (chloroquine-resistant). The crude extracts of the two plants displayed reduced toxicity with an IC50 value of > 47.6 μg/ml, while the compounds from the two plants were cytotoxic with IC50 values ranging between 3.8378-> 4.76 μg/ml against the normal VERO cells. Crude extract of X. americana had mild activity against Cryptococcus neoformans with IC50 value >200 μg/ml. Crude extract of C.nigricans had no activity against Cryptococcus neoformans, while compounds isolated from it exhibited activity with IC50 values ranging from 4.19-8.63 μg/ml. An alkaloid fraction (SAO-07) from X. americana portrayed potent activity against E. coli (IC50 value of 1.45 μg/ml) compared to the control drug Meropenem (IC50 value of 7.57μg/ml). Compounds isolated from C.nigricans had notable activity against methicillin-resistant Staphylococcus aureus with IC50 values ranging between 6.93-16.99 μg/ml in comparison to control drugs whose IC50 values ranged between 2.63-17.57 μg/ml. In conclusion, it was observed that compounds from C.nigricans have antimicrobial activity against methicillin-resistant S. aureus, while an alkaloid isolated from X. americana exhibited activity against E. coli. It was also established that both crude extracts of the two plants had minimal antiplasmodial activity and toxicity while their isolated compounds were cytotoxic. The findings also ascertain that these plants harbour antimicrobial and antiplasmodial compounds and should be further investigated for novel antimalarial and antimicrobial drugs.