BACKGROUND: Medicinal plants have been used for therapeutic purposes and have shown important biological properties. This study aimed to evaluate for the first time the antioxidant activities, total flavonoid, and total phenolic contents of Lavandula mairei Humbert. The ethanol, methanol, ethyl-acetate, and water extracts were used for this purpose.METHODS: The antioxidant activities were assessed in vitro by free radical scavenging activity against 2,2-diphenyl-1-picrylhydrzyl (DPPH), ferric reducing antioxidant power (FRAP), and total antioxidant capacity (TAC). The total flavonoid and phenolic contents were determined spectrophotometrically with gallic acid and Quercetin as standards.RESULTS: In either Soxhlet or maceration methods, the flavonoids and the total phenolic contents were significantly higher in the methanolic extract (P<0.05) compared to other extracts. The total flavonoid content of L. mairei ranged between 119 and 224.6 mg QE/g DW for Soxhlet extracts and from 111.8 to 148.51 mg QE/g DW for maceration extracts. While the total phenolic content was between 35.12 and 99.37 mg GAE/g DW for Soxhlet extracts and 27.63 to 58.99 mg GAE/g DW for maceration extracts. In either the Soxhlet or maceration method, the highest total antioxidant capacity (TAC) was obtained using the ethanolic extract, while the aqueous extract had the highest antioxidant activity for DPPH and FRAP assays.CONCLUSION: These results showed that Lavandula mairei Humbert has great potential to be a promising candidate for natural plant sources of antioxidants.KEYWORDS: Antioxidant activity; Lavandula mairei; Extracts; Maceration; Soxhlet