The Effects of Soil Temperature From Soil Mulching and Harvesting Period On Phenol, Flavonoid And Antioxidant Contents of Java Tea (Orthosiphon Aristatus B.)

Abstract

Purpose: The secondary metabolites of Java tea (Orthosiphon aristatus B) are effective to treat kidney inflammation, kidney stones, and other diseases. Abiotic factors have been known to determine the secondary metabolites contents of Java tea. This study aimed at evaluating the effects of soil temperature resulted from soil mulching and harvesting period on total phenol, flavonoid and antioxidant contents of Java tea. Methods: The research was carried out using nested with completely randomized design under a screen house at Karanganyar, Indonesia from July to December 2019. The first factor was soil mulching (control; black plastic mulch, transparent plastic mulch, biodegradable mulch and rice straw mulch) with three repetitions. The first factor was nested in second factor, namely harvesting period which consisted of two levels, i.e.: 80 and 100 days. The observation parameters were soil temperature of 10-minutes (maximum; mean; minimum and soil temperature based- growing degree days, GDD) with sensors and logger; plant growth (plant height, number of leaves, fresh and dry weight); and secondary metabolites including phenol, flavonoids and antioxidant. Results: The results confirmed the order of the highest to the lowest mean soil temperature was resulted under the transparent plastic mulch> straw > black plastic mulch >control > biodegradable plastic mulch (26.69 > 26.29 > 26.10 > 26.07 > 25.68 oC, respectively). The total phenol, flavonoids and antioxidant produced ranging from 193.75 – 412.50 mg GAE/ 100 g DW; 81.13 – 141.47 mg QE/ 100 g DW; and 1875.5 – 2144.4 µmol TE/g DW.Conclusion: Higher maximum soil temperature resulted into lower phenol content, while higher minimum soil temperature and shorter harvest period increased total flavonoid. Longer harvest period produced more total phenol and antioxidant due to bigger soil temperature based- Growing Degree Day (GDD).