53 Antimicrobial Activity of In Situ Forming Gel Comprising Cork Tree Seed Extract T. Phaechamud and J. Mahadlek Department of Pharmaceutical Technology Faculty of Pharmacy Silpakorn University Nakhon Pathom Thailand J. Charoenteeraboon Department of Biopharmacy Faculty of Pharmacy Silpakorn University Nakhon Pathom Thailand Keywords: methanolic seed extract, anaerobic bacteria, gallic acid, luteolin Abstract Cork tree (Sonneratia caseolaris) is a plant in the family of Sonneratiaceae whose extract has been reported for the traditional use as an astringent and an antiseptic. The methanolic seed extract of cork tree was employed as the active compound in the in situ forming gel containing 30% Eudragit RS in N-methyl pyrrolidone. The prepared gel exhibited the in situ formimg gel properties. The anitimicrobial activity was tested with agar diffusion method using Staphylococcus aureus ATCC 6538, Escherichia coli ATCC 8740, Candida albicans ATCC 17110, Streptococcus mutans ATCC 27175 and anaerobic bacteria from oral cavity as tested microbes. The obtained gel could inhibit all tested microbes. The release of three markers (gallic acid, luteolin glycoside and luteolin) from 10% w/w seed extract gel was performed using dialysis tube method in phosphate buffer pH 6.8. The released amount of three markers was analyzed simultaneously with HPLC method. Gallic acid and luteolin, respectively, were rapidly released in the initial stage and gradually released for 720 min. Luteolin glycoside started to release at 480 min. and lesser amount was released into the medium at 720 min. In situ forming gel comprising cork tree seed extract exhibited the potential dosage form to deliver the active compound from natural product and show antimicrobial activity. INTRODUCTION The clinical signs of periodontitis, which is an inflammatory disease of the teeth supporting tissues are the alteration of the morphology of gingival tissues, bleeding upon probing as well as periodontal pocket formation (Schwach et al., 2000). This pocket area is a suitable site for the anaerobic pathogenic bacteria (Marsh, 1989). Local drug delivery into periodontitis pocket for inhibition of microbial growth is one of periodontitis treatments (Jain et al., 2008). Cork tree (Sonneratia caseolaris L.) family Sonneratiaceae, is found in the less saline parts of mangrove forests often along tidal creeks with slow moving water and on deep muddy soil. By comparison with other mangrove trees, the extract of the cork tree flower and fruit exhibited a relatively high antioxidant activity (Bunyapraphatsara et al., 2003). The antimicrobial activity of cork tree flowers have been reported in comparison with other flower extracts (Wessapan et al., 2007). Previous research has reported that cork tree leaf extracts have antioxidant activities when examined by the DPPH assay, potentially linked to the presence of two flavonoids (luteolin and luteolin 7-O-β- glucoside) that were found to be antioxidants (Sadhu et al., 2006). Some parts of this tree are traditionally used in folklore medicine and include the pounded leaves or fruits as poultices as antiseptic poultices for cuts, sprains and swellings, as well as orally as an astringent and for the treatment of hematuria and small pox, arresting hemorrhage, and the unripe and ripe fruits for coughs and the treatment of parasite infections (Ghani, 2003). Burmese and Indians have applied cork tree as poultice for wounds and bruised wound while Malayans have used peel of mature fruit as anthelmintic and used crushed leaves to heal hemorrhagic urinate symptom (Perry, 1980). From our preliminary study, the methanolic cork tree seed extract exhibit antimicrobial activity therefore, it is Proc. IS on Medicinal and Aromatic Plants Eds.: N. Chomchalow et al. Acta Hort. 1023, ISHS 2014