Objective The research was conducted to determine the physical and chemical properties of guava leaf tea in different years, and analyzed the content and stability of active substances.

Method Gas chromatography-mass spectrometry was used to analyze the aroma components of guava leaf tea; the polyphenol extract from guava leaf tea was concentrated by ethanol soaking and ultrasonic assist, the polysaccharide extract was obtained by water extraction alcoholic precipitation method, and the contents of polyphenols and polysaccharides were determined by Forin-ciocalteu and Phenolsulfuric acid method, respectively. The changes of functional substances in guava leaf tea were analyzed by evaluating antioxidant activity and α-glucosidase inhibitory activity.

Result A total of 69 and 52 aroma components were detected in samples of 2018 and 2019, respectively, as well as polyphenol contents were 34.23 and 40.93 mg/L, and polysaccharide contents were 11.36 and 6.95 mg/g, respectively. The clearance rates of DPPH free radicals were 57.62% and 60.11%, the clearance rates of hydroxyl radicals were 70.49% and 93.58%, the clearance rates of superoxide anions were 22.48% and 23.55%, respectively. The inhibition rates of the two guava leaf teas on α-glucosidase were 94.66% and 79.96%, respectively.

Conclusion The guava leaf tea contains unique aroma, and the longer the storage time, the less polyphenol content and the more polysaccharide content. The antioxidant activity was the strongest when tea brewing time was 30-45 min, and longer storage of guava leaf tea in 2018 showed stronger hypoglycemic activity.