Abstract:The antioxidant activity of phenolic compounds from Adinandra nitida leaves collected in spring and fall and their antiproliferative effects on HepG2 cells were studied. The free/bound polyphenolic contents and free/bound flavonoid contents in Adinandra nitida leaves were investigated by the Folin reagent method and sodium borohydride/chloranil-based assay (SBC), respectively. The in vitro antioxidant activities of free/bound phytochemicals in the extracts and the in vivo antioxidant activities of free phytochemicals in the extracts were measured through oxygen radical absorbance capacity (ORAC), peroxyl radical scavenging capacity (PSC), and cellular antioxidant activity (CAA) assays. The antiproliferative effect of free phytochemicals from Adinandra nitida leaf extracts was measured by the methylene blue colorimetric method. The free phenolic content and free flavonoid content from autumn Adinandra nitida leaves were high, and the values were 142.69 ? 0.58 mg GAE/g DW and 112.98 ? 0.37 CE/g DW, respectively. The ORAC, PSC, and CAA of free phytochemicals from leaf extracts were relatively strong, and the values were 1723.08 ± 109.27 μmol TE/g DW, 24.07 ± 1.98 μM VCE/g DW, and 900.84 ± 2.68 μmol QE/100 g, respectively. The free phytochemicals from autumn Adinandra nitida leaves showed a strong antiproliferative effect on HepG2 cells, with a half maximal effective concentration (EC50) value of 4.30 mg/mL. Adinandra nitida is rich in phytochemicals, and especially, autumn Adinandra nitida leaves are a new raw material for natural antioxidants.
