Proc. Natl. Acad. Sci. USA Vol. 93, pp. 4284-4288, April 1996 Biochemistry Potentiation of the bioavailability of daidzin by an extract ofRadix puerariae (antidipsotropic activity/dose-response curve) WING-MING KEUNG, OSCAR LAzo, LISA KUNZE, AND BERT L. VALLEE Center for Biochemical and Biophysical Sciences and Medicine, Harvard Medical School, 250 Longwood Avenue, Boston, MA 02115 Contributed by Bert L. Vallee, January 2, 1996 ABSTRACT The dose effect of pure daidzin on the sup- these hamsters. Further, two of its isoflavone constituents were pression of ethanol intake in Syrian golden hamsters was purified and also shown to suppress ethanol intake in these compared with that of crude daidzin contained in a methanol animals. Daidzin and daidzein at doses of 150 and 230 mg/kg extract of Radix puerariae (RP). ECso values estimated from per day, respectively, suppress hamster ethanol intake by the graded dose-response curves for pure daidzin and RP '50% (4). Preliminary analyses by HPLC showed that the RP extract daidzin are 23 and 2.3 mg per hamster per day, extract contains only 22 and 2.6 mg/g of daidzin and daidzein, respectively. Apparently the antidipsotropic activity of the RP respectively; comparison of the activity of RP extract to that of extract cannot be accounted for solely by its daidzin content pure daidzin and daidzein indicated that these two known (22 mg/g). In addition to daidzin, six other isoflavones were active principles alone could not account for the total anti- identified in the RP extract and quantified-namely, puerarin dipsotropic activity of the extract. This present study was (160 mg per g of extract), genistin (3.7 mg/g), daidzein (2.6 undertaken to reveal the origin of the additional antidipso- mg/g), daidzein-4',7-diglucoside (1.2 mg/g), genistein (0.2 tropic activity of the methanol extract of RP remaining unac- mg/g), and formononetin (0.16 mg/g). None of these, admin- counted for by daidzin and daidzein. istered either alone or combined, contributes in any signifi- cant way to the antidipsotropic activity of the extract. Plasma AND daidzin concentration-time curves determined in hamsters MATERIALS METHODS administered various doses of pure daidzin or RP extract by RP extract was prepared by refluxing 100 g of fibrous RP i.p. injection indicate that the crude extract daidzin has "10 (Tung Ren Tang Traditional Chinese Medicine Extraction times greater bioavailability than the pure compound. Recon- Factory, Beijing) in 700 ml of methanol for 5 h. The methanol struction of the dose-response effects for pure and crude extract was filtered through Whatman no. 1 filter paper. The daidzin using bioavailable daidzin rather than administered residue was refluxed in 700 ml of fresh methanol for another dose gives a single curve. Synthetic daidzin added to the RP 5 h and also filtered. The combined filtrates were evaporated extract acquires the bioavailability of the endogenous daidzin under vacuum to yield a syrup that was suspended in 200 ml that exists naturally in the extract. These results show that (i) of water and dried to a powder by lyophilization. The extract daidzin is the major active principle in methanol extracts of was analyzed for daidzin, daidzein, daidzein-4',7-diglucoside, RP, and (ii) additional constituents in the methanol extract of puerarin, genistin, genistein, and formononetin by HPLC. The RP assist uptake of daidzin in golden hamsters. column (Beckman C18, 5 ,um, 4.6 mm x 25 cm, IP) was eluted at 1 ml/min with a linear acetonitrile gradient (0-40 min, Pueraria lobata (Willd.) Ohwi or Puerariapseudohirsuta Tan et 12-36%) in 0.1% trifluoroacetic acid. Pure daidzin and daid- Wang (leguminosae) is one of the earliest medicinal plants to zein were synthesized according to published procedures and be used in China. Radix puerariae (RP; root of the Pueraria identified by mass and NMR spectroscopy (5, 6). Daidzein- plant) was first described in the Chinese materia medica, Shen 4',7-diglucoside was synthesized by reacting 1 mol of daidzein, Nong Ben Cao Jing (Anonymous, ca. 200 B.C.), as sweet and 2.1 mol of 2,3,4,6-tetra-0-acetyl-a-D-glucopyranosyl bromide, acrid in taste, cool in nature, and something of a medicinal and 2.1 mol of sodium ethoxide at room temperature for 4 h. panacea: it was used as an antipyretic, antidiarrhetic, dia- Reaction products were precipitated with ethanol and acetyl phoretic, and antiemetic agent-a general antimicrobial agent groups were removed with 1 M NaOH. Reaction side products in today's parlance. In the most celebrated medical treatises of were precipitated by acidification and daidzein-4',7- China, Huang Di Nei Jing (Anonymous, ca. 200 B.C.) and diglucoside in the supernatant was further purified on a Shanghan Lun (Zhang Zhongjing, ca. A.D. 200), RP was semipreparatory HPLC column and identified by NMR and recommended for stiffness and pain of the neck, pain in the mass spectroscopy. Genistein, genistin, formononetin, and eye, "consumptive thirst" (increase in appetite and thirst), and puerarin were products of Indofine Chemical (Somerville, for the induction of early measles eruption (for review, see ref. NJ). Daidzin-supplemented RP extract was prepared by son- 1). Hundreds of years later, medications based on RP and Flos icating 5 g of RP extract and 200 mg of synthetic daidzin in 700 puerariae (flower of the Pueraria plant) were found useful in ml of methanol for 10 min. Methanol was then removed by the treatment of alcohol-related problems, first as an amethys- flash evaporation on a 50°C water bath. RP extract and tic (anti-intoxication) agent (Sun Simiao, ca. A.D. 600) and daidzin-supplemented RP extract contain 22 and 62 mg of later as an antidipsotropic (antidrinking) agent (Li, Dongyuan, daidzin per g dry extract, respectively. ca. A.D. 1200) (for review, see ref. 2). Animal Drinking Experiments. The effect of various agents Recently, we have confirmed the antidipsotropic effect of on ethanol intake was assessed with golden hamsters housed RP in ethanol-preferring Syrian golden hamsters (3). A crude in metabolic cages under a two-bottle free-choice paradigm as methanol extract of RP at a dose of 1.5 g/kg per day signifi- described (3, 4). To determine the dose effects of synthetic cantly suppresses (>50%) the free-choice ethanol intake of daidzin, RP extract, and daidzin-supplemented RP extract on hamster ethanol intake, 45 ethanol-preferring hamsters (121- 130 were used. Before all The publication costs of this article were defrayed in part by page charge g; Sasco, Omaha, NE) drug testing, payment. This article must therefore be hereby marked "advertisement" in accordance with 18 U.S.C. §1734 solely to indicate this fact. Abbreviations: RP, Radix puerariae; AUC, area under curve. 4284 Downloaded by guest on October 1, 2021 Biochemistry: Keung et aL. Proc. Natl. Acad. Sci. USA 93 (1996) 4285 hamsters received (i.p.) 1 ml of sterile phosphate-buffered 100 saline (PBS) each day for 6 days to establish baseline ethanol consumption. They were then divided into nine groups of five animals each and doses for 6 consecutive given daily days (i.p.) 80 of synthetic daidzin, RP extract, or daidzin-supplemented RP I1 extract suspended in 1 ml of sterile PBS. Groups I, II, and III 80> received 6, 18, and 60 mg of synthetic daidzin, respectively; 0 and VI received and 370 of RP 60 - groups IV, V, 37, 111, mg (A extract containing 0.81, 2.44, and 8.1 mg of daidzin, respec- 0 tively; and groups VII, VIII, and IX were given 11, 33, and 111 co4) mg of daidzin-supplemented RP extract containing 0.69, 2.07, CI 40 1 and 6.9 mg of daidzin, respectively. Water and a 15% aqueous ethanol solution were available continuously. Drugs were administered between 3 and 4 p.m. each day and amounts of ethanol consumed were measured between 9 and 10 a.m. The 20 response of each hamster to daidzin or RP extract treatment is expressed as % ethanol intake suppression (% suppression) I I I I given by (Vo - Vd) x 100/Vo, where Vo and Vd are the average 0 I daily intakes of 15% aqueous ethanol solution during the 1 3 10 30 100 baseline and treatment periods, respectively. Throughout this Dose, mg/day study (12 days), hamster weights stayed relatively constant at 124-140 g. Hence, the dosages given were based on an average FIG. 1. Semi-log plot of graded dose-response of ethanol intake body weight of 130 g and were not corrected for the weight of suppression by daidzin administered either as the compound (groups each individual hamster. I, II, and III; open squares) or as a crude RP extract (groups IV, V, Time Course of Plasma Daidzin Concentration and Area and VI; filled squares). Values are mean ± SE for five different Under Curve (AUC). Thirty ethanol-preferring hamsters (121- hamsters. 130 selected as described were used in this g) (3, 4) study. extract is very similar to that of the pure However, Animals were first anesthetized with urethane 1.2 compound. (Sigma; g/kg crude daidzin is 10 times more than the and from each one a 0-time blood was apparently potent pure i.p.) sample (20 ,ul) This can be one or both of the drawn from the orbital venous into a tube 5 compound. finding explained by plexus containing following hypotheses: (i) in addition to daidzin, the RP extract pul of 9% K3EDTA. Animals were then divided into six groups. contains another that could either the Groups I, II, and III were given (i.p.) 6, 18, and 60 mg of pure agent(s) potentiate effect of, or act or with daidzin, and daidzin, respectively.