A radical scavenging guided phytochemical study on the leaf of Simmondsia chinensis afforded ten flavonoids (1–10) and four lignans (11–14). The structures of the isolated compounds were elucidated on the basis of spectroscopic evidences and correlated with known compounds. Among isolated compounds, flavonoid aglycones (1–4) showed stronger antioxidant activity than their glycosides (5–10) whilst lignan glycosides (11–14) showed moderate to weak antioxidant activity using DPPH and -carotene methods in relation to BHT (positive control). The inhibitory potential against enzyme lipoxygenase was also evaluated for isolated compounds exhibiting variable potency. For flavonoids, glycosides are less potent inhibitors than free aglycones. Quercetin is the most potent inhibitor with an IC50 of 5.6 µM. Lignoid glycosides exhibited moderate to weak inhibitory effect against lipoxygenase enzyme. Luteolin was used as a positive control in lipoxygenase inhibiting assay.