Persea americana, Curcuma longa and Allium sativum extracts exhibit cercaricidal, anti-inflammatory and anti-oxidant activities

Introduction Schistosomiasis is a devastating parasitic infection, particularly in Sub-Saharan Africa. Despite the use of Praziquantel, the elimination of schistosomiaisis remains a challenge. The use of medicinal plant as treatment in disease endemic regions has provided a basis for investigating the antischistosomal properties of the plants-derived materials. This study therefore stands as a starting point for the search of new drugs against schistosomiasis. Methods This study sought to evaluate the cercaricidal activity of methanolic extracts of Persea americana, Curcuma longa and Allium sativum. Twenty cercariae were exposed to plant extract concentrations ranging from 3.9 to 103 µg/ml. The antioxidant study was carried out using DPPH, ABTS, and FRAP assays. Anti-inflammatory activity was conducted by assessing the potential through albumin denaturation inhibition assay. The in vitro safety and phytochemical composition of plant extracts were also assessed. Results Cercaricidal tests revealed significant anti-cercariae activity of plant extracts at sublethal concentrations with LC50 values ranging from 7.67 ± 3.40 to 56.07 ± 2.53 µg/ml with C. longa extract being the most potent cercaricidal. Antioxidant activity of plant extracts revealed that methanol extracts of P. americana bark and C. longa have the most potent antioxidant scavenging activities with SC50 values ranging from 91.47 ± 5.83 to 138.75 ± 5.73 µg/ml. Anti-inflammatory analysis showed that plant extracts exhibited most potent anti-inflammatory activity by inhibiting protein denaturation. At 125 µg/ml, A. sativum, C. longa, P. americana root, bark, stem and leaf extracts showed 33.89, 108.26, 93.37, 108.18, 93.96 and 118.15 % inhibitions respectively, while the standard drug Diclofenac sodium (125 µg/ml) produced 24.67 % inhibition. Plant extracts also showed low toxicity on kidney Vero cells and murine macrophage cell lines with IC50 values ranging between 132.15 ± 40.66 and 549.3 ± 43.70 µg/ml. The phytochemical composition of plant extracts shows that the plants are rich in at least five of saponins, cardiac glycosides, phenolics, flavonoids, alkaloids and tannins. Conclusion These results suggest that methanolic extract of C. longa and P. americana showed a potent activity against S. mansoni cercariae with potent antioxidant scavenging activities and can mitigate the inflammatory effect of schistosome eggs within egg-infested tissue, combating the devastating effect of S. mansoni infection.