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Litchi (Litchi chinensis Sonn.) is a well-known traditional medicine since ancient times. The crude extract of litchi leaf exhibited good bioactivity against cancer cells. In this work, three sesquilignans, ehletianol C (1), sesquipinsapol B (2) and sesquimarocanol B (3), and one lignan glycoside schizandriside (4) were isolated from the ethyl acetate-soluble extract of litchi leaf by column chromatography. Their structures were further elucidated by ESI-MS and NMR spectral studies. Ehletianol C, sesquipinsapol B and sesquimarocanol B were detected from this species for the first time. Sesquipinsapol B (EC50 values less than 2.0 μg/mL) and sesquimarocanol B (EC50 values less than 2.4 μg/mL) showed very high cytotoxicities against nasopharynx carcinoma cells CNE1 and CNE2 cells, respectively. Thus, they could be utilized as good drug candidates against nasopharynx cancer. Moreover, three sesquilignans showed effective in vitro cytotoxicities against human cancer cells HepG2 and Hela. Four lignans showed better antioxidant activities than butylated hydroxytoluene (BHT).

Six flavonoids, namely luteolin (1), epicatechin (2), kaempferol 3-O-β-glucoside (3), kaempferol 3-O-α-rhamnoside (4), procyanidin A2 (5) and rutin (6) were purified from the EtOAc-soluble extract of litchi leaf by column chromatography. Their structures were elucidated by nuclear magnetic resonance (NMR) spectroscopy and mass spectrometry (MS) evidences. Luteolin and kaempferol 3-O-α-rhamnoside were found from this plant for the first time. Procyanidin A2 exhibited high anticancer activities against human hepatoma HepG2 and human cervical carcinoma Hela cells. However, it had poor anticancer activities against human lung cancer A549 and human breast cancer MCF-7 cells. Luteolin, epicatechin, procyanidin A2 and rutin showed good antioxidant activities than butylated hydroxytoluene (BHT). The antimicrobial activity assay indicated that luteolin possessed the strongest antimicrobial activity against Staphylococcus aureus, Escherichia coli, Shigella dysenteriae, Salmonella and Bacillus thuringiensis. Epicatechin, procyanidin A2 and rutin showed relatively weak antimicrobial activities.

Litchi leaf is a good resource for phenolics, which are good candidates for medicines. In this work, three phenolics were isolated from litchi leaf by column chromatography. Their structures were identified by electrospray ionization–mass spectrometry (ESI-MS) and nuclear magnetic resonance (NMR) spectroscopy as secoisolariciresinol 9′- O - β - D- xyloside ( 1 ), 4,7,7′,8′,9,9′-hexahydroxy-3,3′-dimethoxy-8,4′-oxyneolignan ( 2 ), and cinnamtannin B1 ( 3 ). Cinnamtannin B1 showed better extra- and intracellular antioxidant activities than Compounds 1 and 2 . The intracellular antioxidant activity of cinnamtannin B1 was related to the upregulation of endogenous antioxidant enzyme activities (superoxide dismutase, catalase, and glutathione peroxidase), and inhibition of ROS generation. Furthermore, cinnamtannin B1 exhibited strong antiproliferative effects against HepG 2 and Siha cell lines with no significant cytotoxicities. In the case of the HepG 2 cell line, cell cycle arrest and apoptosis induction were the underlying anticancer mechanisms of cinnamtannin B1. The results indicated that cinnamtannin B1 was a potent cancer cell proliferation inhibitor and a good intracellular antioxidant. [ABSTRACT FROM AUTHOR]

Highlights: [•] Sesquipinsapol B showed very high cytotoxicity against nasopharynx cancer. [•] Ehletianol C, sesquipinsapol B, sesquimarocanol B, and schizandriside were identified. [•] Three sesquilignans showed good cytotoxities against HepG2 and Hela cells. [Copyright &y& Elsevier]

Highlights: [•] The structure of flavonoids in litchi leaf were identified by NMR. [•] Procyanidin A2 exhibited good cytotoxicities against HepG2 and Hela cells. [•] Luteolin showed strong antimicrobial activities. [•] All flavonoids were found to have good antioxidant activities. [Copyright &y& Elsevier]