Objective: To determine the best temperature and time of fermentation for making soybean (Glycine max (L.) Merril) tempeh seeds with high content of isoflavones. Methods: Five varieties of soybean seeds, Devon-1, Dena-1, Dega-1, Anjasmoro, and Argomulyo, were determined for their isoflavones content using an Ultraviolet (UV) spectrophotometer. A variety containing the highest isoflavones was washed, boiled, peeled, then mixed with tempeh starter (Rhizopus oligosporus culture) at 1 g/kg. The mixture was then poured into plastic bags and flattened with two centimeters of thickness. Fermentation in three conditions: (a) ambient temperature (27-32 °C) without air circulation, (b) 27±0.5 °C, and (c) 30±0.5 °C both with air circulation. The inner temperature, ripening time, and rotting time was recorded. The total isoflavones content was measured every 6 h. Results: The variety of Devon-1 has the highest content of isoflavones (0.112% w/w). Fermentation in condition (a) caused the tempeh too hot(42 °C) and rotted at the 42nd h. Condition (b) produced the best tempeh, ripening at the inner peak temperature (32.5 °C) at the 32nd h; and rotted after the 100th h. Condition (c) produced good tempeh; the ripening occurred at the 31st h at 33 °C and rotted after the 113th h. Tempeh that was produced with condition (b) at the 72nd h has the highest content of isoflavones (0.089% w/w). Conclusion: Fermentation at 27±0.5 °C with air circulation for 72 h produced tempeh with the highest isoflavones content (0.089% w/w), but decrease about 20% compared to its content in seeds (0.112% w/w).

Abstract. Aryantini D, Astuti P, Yuniarti N, Wahyuono S. 2023. Bioassay-guided isolation of the antioxidant constituent from Kaempferia rotunda L. Biodiversitas 24: 3641-3648. Kaempferia rotunda L. contains various phytochemical compounds with various biological activities and has been widely utilized in traditional medicine. This research focused on exploring bioactive compounds in the ethanol extract of Kaempferia rotunda using radical scavenging (1,1-Diphenyl-2-picrylhydrazyl) bioassay-guided isolation. Initially, the powdered material of K. rotunda was macerated with 70% ethanol and filtered, and the filtrate was evaporated in vacuo to make concentrated ethanol extract. The concentrated ethanol extract was then triturated gradually with increasing polarity of solvents (n-hexane, ethyl acetate, ethanol) to give n-hexane (HSF), ethyl acetate (EASF), ethanol (ESF), and residue (ISF) fractions. Each fraction was tested by DPPH bioassay with quercetin as the positive control to determine the active fraction. The active fraction (ESF) was further fractionated by Vacuum Liquid Chromatography (VLC) using a mobile gradient phase starting from ethyl acetate 100%, acetone 100%, and methanol 100% tomake3 sub-fractions (F1, F2, F3),respectively. The DPPH radical scavenging bioassay showed that F1 was the most active, containing bioactive compound detected by TLC visualized by DPPH. Based on spectroscopic and literature data comparison, this compound was isolated, purified, and identified ascrotepoxide. Crotepoxide displayed IC50of 38.91±0.59 (ABTS), 47.45±0.60 (DPPH),and 26.74±1.23 (FRAP) µg/mL.