Optimization of Extraction Process of Flavonoids and Polyphenols from Perilla frutescens (L.) Britt Leaves and Comparison of Antioxidant Activities of Different Varieties

Perilla frutescens (L.) Britt. is one of the edible and medicinal plants. The purpose of this study was to compare the flavonoids and polyphenols extracted from different varieties of P. frutescens leaves ('Korean green PF1', 'Chinese PF2', 'Korean purple PF3', 'Korean bicolor PF4', 'Chinese bicolor PF5'), and to explore their antioxidant activities in vitro. Optimization of extraction process of flavonoids and polyphenols from P. frutescens leaves was studied by single factor tests and orthogonal test. The results showed that the optimum parameters were ethanol concentration 75%, solid-liquid ratio 1:80 g/mL, extraction time 2 h, extraction temperature 70 ℃. Under these conditions, the extraction amount of flavonoids and polyphenols was the highest, which were (16.82±0.60) mg/g and (80.42±2.66) mg/g, respectively. Among different varieties of P. frutescens leaves, PF3 had the highest content of polyphenols (17.77±0.29) mg/g, PF5 had the highest content of flavonoids (80.42±2.66) mg/g. The results of antioxidant activity showed that the leaves of different varieties of P. frutescens had good antioxidant activity. Among them, the ABTS⁺ free radical scavenging rate (IC₅₀ 150.31±2.46 μg/mL), DPPH free radical scavenging ability (IC₅₀ 88.04±3.61 μg/mL) and total reducing power of PF5 were the strongest (P<0.05). Correlation analysis showed that polyphenol extraction amount was significantly correlated with ABTS⁺ free radical scavenging rate and total reducing power (P<0.05), flavonoids extraction amount was significantly correlated with DPPH free radical scavenging rate and ABTS⁺ free radical scavenging rate (P<0.05), and was extremely significant with total reducing power (P<0.01). This study would provide a theoretical basis for the development and utilization of different varieties of P. frutescens leaf resources.