- The project “Isolation of biological active components from essential oils and medicinal plants indigenous to Thailand” is the project under the Center of research and development for value increase of folkloric plants. The studies are divided into two sections as follows. 1. Essential oils Thirteen Thai essential oils, turmeric, phlai, holy basil, sweet basil, pomelo, fingerroot, galanga, kaffir lime leaf, kaffir lime peel, citronella, black pepper, guava leaf, betel leaf vine oils, were submitted to antimicrobial (enteric bacteria and histamine producing bacteria), antioxidant, antiacetylcholinesterase, antiinflammatory, -amyloid aggregation inhibition activities. The results are as follows. 1.1. Lemongrass, kaffir lime leaf, betel leaf vine, holy basil and sweet basil oils exhibited antibacterial activity against enteric bacteria. GC-MS and TLC bioautography indicated that the active components of the oils were citral, citronellal, eugenol and methyl eugenol, methyl chavicol, respectively. 1.2. Clove, lemongrass and sweet basil oils showed antibacterial activity against histamine producing bacteria with eugenol, citral, and methyl chavicol as active components, respectively. 1.3. All essential oils tested showed antioxidant activity. Betel leaf vine oil exhibited strongest activity followed by holy basil oil. The active components of both oils were eugenol. 1.4. Black pepper, galanga, turmeric and fingerroot oils showed strong antiacetylcholinesterase activity with 3--carene, cineole and caryophyllene, cineole and caryophyllene, camphor and cineole, respectively. 1.5. The essential oils with strong antioxidant activity were subjected to anti-inflammatory testing and found betel leaf vine oil exerted strongest NO production inhibition (89.27%) followed by lemongrass, holy basil and kaffir lime leaf oils. Betel leaf vine oil exhibited strongest IL-6 production inhibition (68.05%) followed by kaffir lime leaf, holy basil and galanga oils. Holy basil oil also showed strongest activity on inhibition of TNF- production. The active constituents of the essential oils were eugenol, transcaryophyllene, 1,8-cineole, citronellal, citral, methyl chavicol and methyl eugenol. 1.6. The essential oils which inhibited -amyloid aggregation more than 50% were betel leaf vine (63.30%), galangal (59.44%) and fingerroot (57.95%) oils. Among the compounds tested camphene exhibited strongest activity (87.50%) followed by eugenol (60.83%), trans-caryophyllene (59.82%), linalool (59.50%), limonene (54.13%), 3--carene (53.00%) and (+)-camphor (51.91%). 2. Folkloric Plants Three plants, Khae-na, Cha-om and Kan phai Mahidol were selected for the isolation of bioactive compounds. ฐ 2.1. Khae-na Bioguided separation of Khae-na found 6 antioxidant compounds, hallerone, protocatechuic acid, rengynolone, cleroindicin B, ixoside and laminaribiose. Ursolic acid showed strong antiacetylcholinesterase activity while tetracosane and the mixture of -sitosterol and stigmasterol exhibited weak activity. 2.2 Cha-om Cha-om exhibited antiacetylcholinesterase and antioxidant activities. Four antiacetylcholinesterase, methyl tridecanoate, arborinone, tetracosane and 4,8-dimethylnonacosane were isolated from hexane extract with weak activity. New antiacetylcholinesterase, 4-methoxytetrahydrofuran-2-carboxylic acid was isolated from methanol extract. Volatile oil obtained from steam distillation of Cha-om showed antioxidant activity. Chromatographic separation and identification by GC-MS revealed four antioxidant and antiacetylcholinesterase compounds, 3-hexyl hydroperoxide, 1,3,5,-trithiane, 3,5-dimethyl-1,2,4-trithiolane and 5,6-dihydro-2,4,6-trimethyl-4H-1,3,5-dithiazine. 2.3 Kan phai Mahidol Kan phai flower exhibited antioxidant acitivity stronger than other biological activities tested and ethyl acetate fraction showed strongest activity. Five active compounds, kaempferol, kaempferol-3-O--Larabinoside and -arbutin along with two inactive compounds, 3-O-methylinositol and daucosterol were isolated from ethyl acetate extract. And the last two compounds were also isolated from methanol.