Secondary Metabolite Profiling, In Vitro Antimicrobial Activity Evaluation, and In Vivo Acute Toxicity Assessment of Osyris quadripartita and Toddalia asiatica Leaves and Stem Bark Extracts.

In Ethiopia, Osyris quadripartita (Santalaceae) and Toddalia asiatica (Rutaceae) are traditionally used to treat malaria, skin and stomach disorders, and other tropical diseases. This study screened the major secondary metabolite profiles and evaluated the in vitro antimicrobial and in vivo acute toxicity effects of chloroform and methanol extracts from the leaves and stem barks of O. quadripartita and T. asiatica. Secondary metabolite profiling was conducted according to the standard protocols. The in vitro antimicrobial activity evaluation was performed using Kirby-Bauer and broth dilution assays. The in vivo acute toxicity was assessed in experimental mice, grouped into experimental and control groups. Detected phytochemicals included tannins, alkaloids, saponins, flavonoids, and terpenoids, while phlobatannins were absent. Methanol stem bark extracts of O. quadripartita and T. asiatica showed higher inhibition zones of 10.67 ± 0.57 and 10.6 ± 0.11 mm, respectively, against methicillin-resistant Staphylococcus aureus at a minimum concentration of 100 mg/mL. These extracts also showed the lowest MIC values against S. aureus (6.25 ± 00 mg/mL) and S. pyogenes (12.5 ± 00 mg/mL), respectively. The methanol leaf extract of O. quadripartita and stem barks of T. asiatica demonstrated MBC values of 25 and 50 mg/mL, respectively, against S. pyogenes. A higher antifungal effect was observed with the methanol leaf extract of T. asiatica against Aspergillus niger (8.33 ± 0.28 mm at 100 mg/mL). The present findings revealed that methanol extracts of both plants exhibited better antimicrobial activity than the chloroform extracts, as evidenced by the lowest MIC and MBC values. This aligns with the presence of polar secondary metabolites in methanol extracts, which may be responsible for the observed activity. All crude extracts from both plants showed no signs of toxicity at doses up to 2000 mg/kg in experimental mice, indicating the absence of acute toxicity. In conclusion, these findings support the traditional therapeutic use of the leaves and stem barks of O. quadripartita and T. asiatica as antimicrobial agents. Further research is needed to quantify the major classes of phytochemicals and identify the compounds responsible for antimicrobial activity using FT-IR, LC-MS, and NMR instruments.