Xanthopterin, an unconjugated pteridine compound, is the main component of the yellow granule in the Oriental hornet bear wings, produces a characteristic excitation/emission maximum at 386/456 nm^[2]. Xanthopterin (XPT) causes renal growth and hypertrophy in rat^[1]. Xanthopterin inhibits RNA synthesis^[4]. In Vitro: Xanthopterin (7.8-250 mM; 24 hours) show a significant reduction in mitochondrial activity with respect to controls (IC₅₀=109 mM)^[2].