title: Anti-allergic substances from the rhizomes of Dioscorea membranacea.
abstract: Extracts of five species of Thai medicinal plants, locally known as Hua-Khao-Yen, were screened for anti-allergic activities using RBL-2H3 cells. Of the five species studied, the ethanolic extract of Dioscorea membranacea exhibited potent inhibitory activity against beta-hexosaminidase release as a marker of degranulation in RBL-2H3 cells, with an IC(50) value of 37.5microg/mL. Eight compounds were isolated from this crude ethanolic extract, [two naphthofuranoxepins (1,2), one phenanthraquinone (3), three steroids (4-6), and two steroidal saponins (7,8)], and tested for their anti-allergic activities. The results showed that dioscorealide B (2) possessed the highest activity with an IC(50) value of 5.7microM, followed by dioscoreanone (3, IC(50)=7.7microM), dioscorealide A (1, IC(50)=27.9microM), and diosgenin (9, IC(50)=29.9microM). Structure-activity relationship studies of naphthofuranoxepins on anti-allergic activity revealed that the hydroxylation at position 8 conferred higher activity than methoxylation. For diosgenin derivatives, the aglycone was found to possess higher activity than the diglucosylated molecule; whereas substitution with rhamnoglucosides apparently results in loss of activity. Furthermore, effects of dioscorealide A, dioscorealide B, and dioscoreanone on antigen-induced release of TNF-alpha and IL-4 in the late phase reaction were also examined.
authors.affiliation: Department of Pharmacognosy and Pharmaceutical Botany, Faculty of Pharmaceutical Sciences, Prince of Songkla University, Hat-Yai, Songkhla 90112, Thailand. supinyat@yahoo.com
authors.forename: Supinya
authors.initials: S
authors.lastname: Tewtrakul
authors.forename: Arunporn
authors.initials: A
authors.lastname: Itharat
mesh_terms: D000818:Animals; D018926:Anti-Allergic Agents / Q000737:chemistry / Q000302:isolation & purification / Q000494:pharmacology*; D015550:Cell Degranulation / Q000187:drug effects* / Q000502:physiology; D002460:Cell Line; D027742:Dioscorea / Q000737:chemistry*; D004144:Diosgenin / Q000737:chemistry / Q000302:isolation & purification / Q000494:pharmacology*; D006576:Heterocyclic Compounds, 4 or More Rings / Q000737:chemistry / Q000302:isolation & purification / Q000494:pharmacology*; D015847:Interleukin-4 / Q000037:antagonists & inhibitors / Q000378:metabolism; D010616:Phenanthrenes / Q000737:chemistry / Q000302:isolation & purification / Q000494:pharmacology*; D010936:Plant Extracts / Q000737:chemistry / Q000302:isolation & purification / Q000494:pharmacology*; D011809:Quinones / Q000737:chemistry / Q000302:isolation & purification / Q000494:pharmacology*; D051381:Rats; D027343:Rhizome / Q000737:chemistry*; D012503:Saponins / Q000737:chemistry / Q000302:isolation & purification / Q000494:pharmacology*; D013329:Structure-Activity Relationship; D001619:beta-N-Acetylhexosaminidases / Q000037:antagonists & inhibitors
chemical_list: D018926:Anti-Allergic Agents; D006576:Heterocyclic Compounds, 4 or More Rings; D010616:Phenanthrenes; D010936:Plant Extracts; D011809:Quinones; D012503:Saponins; C516705:dioscorealide A; C516706:dioscorealide B; C516707:dioscoreanone; D015847:Interleukin-4; D001619:beta-N-Acetylhexosaminidases; D004144:Diosgenin