Phytochemical screening, in vivo antibacterial and antioxidant activities of roots of Euclea mayottensis H. perrier and fruits of Tambourissa comorensis D.H. Lorence

Abstract

There is increased antimicrobial drug resistance as common antibiotics are no longer effective. In Africa and Comoros in particular the use of medicinal plants as a remedy for the common bacterial infections is on the rise. Euclea mayottensis and Tambourissa comorensis are two endemic medicinal plants from the Archipelago of Comoros. They are used to treat different ailments including bacterial infections. However, the scientific basis of their use as medicinal remedies is still lacking. This study, therefore, aimed at identifying the phytochemicals present in E. mayottensis and T. comorensis as well as determining their antimicrobial and antioxidant activities.

Maceration method was used for the extraction process using distilled water, ethanol and ethyl acetate as solvents. The qualitative phytochemical screening was done using standard procedures. Total phenolic content (TPC) was determined using the Folin-Ciocalteu method. The antibacterial activity was determined using the agar well diffusion method, the minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) was established using the broth microdilution assay. The antioxidant activity was determined using the DPPH radical scavenging activity and the ferric reducing antioxidant power (FRAP) methods.

The screening of the root extracts of E. mayottensis and fruit extracts of T. comorensis revealed that both plants are rich in phytochemicals. The highest TPC value was seen in the ethanolic extracts of both E. mayottensis (1.22 mg GAE/g dry extracts) and T. comorensis (0.89 mg GAE/g dry extracts). The antibacterial activity showed that both plants have a promising inhibitory effect on all the strains used with diameter of inhibitions varying from 6.6 to 20 mm. The highest MIC value was observed in the ethanolic extracts of both plants (0.16 mg/ml). The DPPH assay showed that the water extracts had the highest scavenging effect (51.42% for T. comorensis and 44.6% for E. mayottensis). The FRAP assay showed a promising reducing power of all the extracts. E. mayottensis ethanolic extract showed the highest reducing power (0.543-0.908) while for T. comorensis the highest value was observed in the ethyl acetate extract (0.329-0.773).

In conclusion, the study showed that the presence of the different phytochemicals as well as their great antibacterial and antioxidant activities may explain the therapeutic effects exhibited by E. mayottensis and T. comorensis and gives a scientific basis for their use in the community. Further studies to isolate and identify the bioactive compounds and assess the bioactivities of the extracts in vivo is recommended.