Standardized Bioflavonoid Compositions as Analgesics 157 and quercetin in hot plate test (Rylski, Duriasz-Rowinska, & Rewerski, 1979) have shown variable degrees of analgesic activity. Dose-dependent antinociceptive activ- ity was also observed in acacia honey-treated mice in tail-flick and paw-withdrawal tests (Azim, Perveen, Mesaik, & Simjee, 2007). Similarly, in structure-activity study, some methoxy derivatives of flavone showed antinociceptive effect in acetic acid writhing and tail-flick mouse models (Thirugnanasambantham et al., 1993). The anti-inflammatory properties of both baicalin and catechins have been widely reported. However, the reports of analgesic effects of baicalin and catechins are limited. The primary objective of this study is to document the analgesic abil- ity of a standardized bioflavonoid composition with a combination of baicalin and catechins on three different animal models. Statistical Analysis The results are represented as mean ± SD and percent changes. Statistical signifi- cance between two groups was calculated by means of analysis of variance followed by student’s t-test. Results were considered to be statistically significant if P ≤ .05. MATERIALS AND METHODS Preparation of UP446 Detailed method for preparation of the two major flavonoids, baicalin and catechin, from the roots of S. baicalensis and the heartwoods of A. catechu, respectively, were disclosed in a US patent (Jia, 2007). Briefly, S. baicalensis extract from roots was extracted with water and then recrystallized. The S. baicalensis extract contained baicalin as the major bioflavonoid at content not less than 75% as well as other minor free-B-ring flavonoids such as wogonin-7-O-G-glucuronide, oroxylin A-7-O- G-glucuronide, and baicalein. Catechin extract was obtained from repeated crys- tallization of an aqueous extraction of the heartwoods of an India medicinal plant, A. catechu. (+)-Catechin is the major component in the A. catechu extract with a content of not less than 65% plus a minor amount of its enantiomer, epicatechin, as well as other minor amounts of flavans. Analyses of the extracts were performed separately by two high-performance liquid chromatography (HPLC) methods. The quantification results of baicalin, from the S. baicalensis extract and catechin from the A. catechu extract were cal- culated by comparison HPLC peak area with known standards. The final UP446 composition was a mixture of S. baicalensis and A. catechu standardized extracts at a ratio 4:1 with baicalin content not less than 60% and catechin content not less than 10%. Other minor flavonoids, such as wogonin 7-glucuronide and baicalein, account for about 15% of total weight. Moisture, ash, fat, and fiber constitute the remainder weight. The combined flavonoid content was analyzed by HPLC using a Phenomenex Luna 5µ C-18, 250 mm × 4.6 mm with a C-18 Security Guard cartridge in a column oven at 35◦C. The mobile phase had a flow rate of 1.0 ml/min and used an isocratic 1% phosphoric acid:acetonitrile ratio of 85%:15% for the first 7 min and then a new gradient to 10%:90% from 7 min to 16.5 min and then an isocratic 1% phosphoric acid:acetonitrile gradient with a ration of 85%:15% for 7.5 min. The