Journal of Food Science and Engineering 1 (2011) Determination of Genistein in the Fermented By-product of Soybean Curd, an Indonesian Food, and Its in vivo Assay on Carrageenan-Induced Mice R. Mustarichie, J. Levita*, I. Musfiroh, M. Moektiwardoyo Pharmacochemistry Division, Faculty of Pharmacy, Universitas Padjadjaran, Jl. Raya Bandung-Sumedang Km 21, Sumedang, West Java 45363, Indonesia Received: August 26, 2011 / Published: October 20, 2011. Abstract: In our country, Indonesia, especially in West Java, people frequently consume fermented by-product of soybean curd for their main course. The by-product of curd, usually is discarded, can be fermented using either Neurospora (Neurospora sitophila) or Rhizopus (Rhizopus oligosporus) yeast to make oncom. Genistein is a phytoestrogen, an estrogen-like chemical compound present in plants, that has anti-inflammatory property. Genistein can be determined by UV spectrophotometric method based on the UV absorbance of its complex with aluminum chloride. Addition of acid is a critical point in the procedure. The aim of this research was to know whether genistein is still contained in oncom. This research also studied about oncom’s activity on carrageenan-induced mice. Acetosal was used as drug control. Result showed that genistein was detected contained in oncom extract. The in vivo assay indicated that oncom extract (dose 1,000 mg/kg of body weight) reduced oedema in carragenan-induced paw of mice, which potencies were 0.66 times lower than that of acetosal’s. Oncom might be useful as food and as a weak inflammation reducer as well. Key words: Antiinflammatory activity, fermented by-product of soybean curd, genistein; Indonesian food, oncom. 1. Introduction In our country, Indonesia, especially in West Java, people frequently consume fermented by-product of soybean curd (Fig. 1) for their main course. The by-product of soybean curd, usually is discarded, can be made edible-worth by fermentation using either Neurospora (Neurospora sitophila) or Rhizopus (Rhizopus oligosporus) yeast. The food produced is called oncom. Oncom is delicious and affordable, therefore it has become a favourite food in Sundanese area (West Java) for decades. Sundanese people usually fry the oncom in a small volume of cooking oil with the addition of tomato slices, paprika, chopped salty fish, and other spices. In this work, we use *Corresponding author: Dr. Jutti Levita, lecturer and researcher. Research field: food and pharmaceutical analysis-medicinal chemistry-molecular pharmacology. E-mail: la_via63@yahoo.com ; jutti.levita@unpad.ac.id Neurospora fermented by-product of curd, named red oncom. Fig. 1 Fermented by-product of soybean curd, called oncom. Genistein (Fig. 2) is a phytoestrogen, an estrogen-like chemical compound present in plants, especially Leguminoceae, that binds to estrogen