Metabolomic Profiling of Taiwanese Roselle (Hibiscus sabdariffa) Leaves and Their Antiproliferative and Insulin Resistance-Ameliorating Potential

Roselle (Hibiscus sabdariffa) leaves are the major by-product after harvesting the commercial calyces, and they contain diverse functional metabolites such as phenolic acids and flavonoids. This study aimed to comprehensively characterize the metabolite profiles of the leaves of two Taiwanese roselle varieties (Taitung No. 6 and Taitung No. 3) and to evaluate their antiproliferative and insulin resistance-ameliorating activities. Extracts prepared with 50% EtOH and n-hexane were analyzed by untargeted and targeted LC-MS/MS and GC-MS, respectively. Results revealed that the 50% EtOH extracts of both varieties were rich in neochlorogenic acid, cryptochlorogenic acid, rutin, and nicotiflorin. Taitung No. 6 uniquely contained higher levels of anthocyanins including delphinidin-3-O-sambubioside and cyanidin-3-O-sambubioside. Acidified 50% EtOH extraction increased flavonoid aglycone and polyamine contents. n-Hexane extracts were identified as potential sources of vitamin E, α-linolenic acid, squalene, and phytol. Both varieties exhibited antiproliferative activity against BxPC-3 pancreatic cancer cells (IC50: 289.2–356.8 μg/mL) and significantly improved the glucose uptake in insulin-resistant HepG2 cells. Neochlorogenic acid and cryptochlorogenic acid were identified as primary active contributors to these bioactivities. This study elucidated the metabolite composition of Taiwanese roselle leaves and provided a scientific basis for the utilization of roselle leaves as a promising functional ingredient.