Dose-dependent Additive And Antagonistic Effects on Phenolics, Tannins, Flavonoids, And Antioxidant Activity Of Platycladus orientalis (L.) Franco In Binary Mixtures With Selected East Asian Medicinal Plants

Abstract

This study compared the phytochemical profiles and antioxidant activity of Platycladus orientalis when individually combined in a 1:1 ratio with Phyllanthus urinaria, Strobilanthes crispus, and Folium mori. The types of antioxidant interactions (synergistic, additive or antagonistic) in the combined plant samples were evaluated using both experimental and theoretical antioxidant capacity models. P. urinaria exhibited the highest phenolic content, reducing power, and radical scavenging potential, whereas S. crispus showed the lowest levels of phenolics, flavonoids, and antioxidant activity in the single-plant analysis. Pairing P. orientalis with the three selected medicinal plants resulted in either antagonistic or additive antioxidant effects, depending on the plant species and the sample concentration used. S. crispus contributed to the highest percentage of combined samples exhibiting an additive effect on total phenolic content, tannin levels, and reducing activity. The reducing activities of the combined plant samples were positively correlated with phenolic (r = 0.981) and flavonoid (r = 0.906) content, with high statistical significance (p < 0.0001). Pairing P. orientalis with either S. crispus or P. urinaria resulted in a relatively strong additive effect on reducing activity. Among the 108 combined plant samples, the mixture of P. orientalis (6.4 mg/mL) and S. crispus (6.4 mg/mL) exhibited the highest antioxidant index (97%) and an additive effect on overall phenolic content.