Evaluation of Interleukin-8 (IL-8) Expression in Human Aortic Endothelial Cells (HAECs) and Antioxidant Activity of Isolated Compounds from the Endemic Hawaiian Plant Pipturus albidus (Māmaki)

Pipturus albidus (commonly known as māmaki) is an endemic Hawaiian plant traditionally consumed as a medicinal herbal tea; however, its comprehensive potential for phytochemical composition and biological activities remains underexplored. In this study, we present the first comprehensive phytochemical characterization of the ethanol extract of P. albidus, identifying twelve compounds through chromatographic and spectroscopic analyses. The isolated compounds were subjected to a series of antioxidant assays, including 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging, ferric reducing antioxidant power (FRAP), and oxygen radical absorbance capacity (ORAC). Cinchonain Ia (2), vitexin (6), and (7S,8R)-dihydrodehydro diconiferyl alcohol (11) demonstrated strong free radical-scavenging and reducing capacities. Evaluation of Interleukin-8 (IL-8) expression in TNF-α-stimulated human aortic endothelial cells (HAECs) revealed that catechin-(7,8-bc)-4a-(3,4-dihydroxyphenyl)-dihydro-2(3H)-pyranone (3) and trans-ferulic acid (9) significantly increased IL-8 mRNA expression (p < 0.05), indicating potential pro-inflammatory effects of these isolated constituents. In contrast, neither the crude extract (PE) nor vitexin (6) produced a statistically significant difference in IL-8 mRNA levels compared to the TNF-α control (p < 0.05). Quantitative LC-MS/MS analysis confirmed that caffeine, theobromine, theophylline, and EGCG were below the limit of detection in P. albidus leaf extracts, indicating that P. albidus possesses a phytochemical constituent distinct from that of green tea. In summary, P. albidus leaves contain unique phytochemicals with cell-free antioxidant activity, while cell-based assays indicate potential pro-inflammatory risks for compounds 3 and 9 and no significant anti-inflammatory suppression by PE or vitexin (6).