PTPN1 and diabetes mellitus: Chen et al. (2021) found that γ-MG inhibited α-amylase/ α-glucosidase through insulin sensitization, promoted glucose intake, and reduced sugar digestion, thus exerting an anti-hyperglycemic activity. Protein tyrosine phosphatase 1B (PTP1B) is an action site for diabetes medicines. Hu et al. (2021) reported that garcinone E, a xanthone of mangosteen, effectively inhibited the activity of PTP1B. Moreover, Watanabe et al. (2018) found that a mangosteen extract significantly improved the insulin sensitivity of insulin-resistant obese female patients without side effects.