Polyphenols in Litchi (Litchi chinensis Sonn.) Seeds: Comparison of Profiles Among Five Cultivars and Evaluation of Anti-Inflammatory, Analgesic Potentials

Abstract

Litchi seeds are by-products produced from the fruit consumption, which contain rich phenolic compounds and have been traditionally used in inflammatory pain relief. This study sought to reveal phenolic profiles in the litchi seeds from different cultivars and explore their contributions to anti-inflammatory, analgesic potentials. Purified polyphenols were derived from five cultivars of litchi seeds, including Baitangying (BTY), Baila (BL), Feizixiao (FZX), Heiye (HY), and Huaizhi (HZ). Fifteen flavonoids, two phenolic acids, one coumarin, and two tannins were characterized using UPLC-Q/TOF-MS, while procyanidin A₁, procyanidin A₂, and phlorizin were identified as major phenolic compounds in HPLC. HY contained relatively higher phenolic contents. The polyphenols from different cultivars effectively inhibited LPS-induced generation of ROS, NO, IL-6, TNF-α, and PGE₂ in RAW 264.7 macrophages, which was tightly associated with the contents of procyanidin A₁, procyanidin A₂, and phlorizin. Procyanidin A₁ played a relatively significant role, which could strongly bind to iNOS, COX-2 and their mixture with procyanidin A₂ and phlorizin exhibited better effect in the NO inhibition. Furthermore, the litchi seed polyphenols were demonstrated to inhibit xylene-induced ear edema and acetic acid-induced abdominal writhing in mice. Thus, the litchi seed polyphenols possessed potentials to be utilized as anti-inflammatory and analgesic agents.