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Four known coumarins, dentatin (1), nor-dentatin (2), clausenidin (3) and xanthoxyletin (5), and six known carbazole derivatives, 3-formylcarbazole (6), mukonal (7), 3-methoxycarbonylcarbazole (8), murrayanine (9), 2-hydroxy-3-formyl-7-methoxycarbazole (10) and clauszoline J (11) were isolated from Clausena excavata. Compounds 1 and 6 were first isolated from the crude chloroform extract of the rhizomes. Compounds 1, 2, 3, 6, 7, 8, 10 and 11 showed antimycobacterial activity at a minimum inhibitory concentration (MIC) of 50, 100, 200, 100, 200, 50, 100 and 100 microg/mL, respectively. O-Methylated clausenidin ( 4), prepared from 3, exhibited antimycobacterial activity at MIC 50 microg/mL. Compounds 6, 7, 8 and 10 showed antifungal activity with IC 50 values of 13.6, 29.3, 9.5 and 2.8 microg/mL, respectively. All compounds demonstrated no cytotoxicity against KB and BC-1 cell lines.

Three carbazole derivatives, O-methylmukonal (1), 3-formyl-2,7-dimethoxycarbazole (2) and clauszoline J (3), and a pyranocoumarin, clausenidin (4), were isolated from the rhizomes and roots of Clausena excavata. Compound 1, isolated from this plant for the first time, has not been reported previously as having anti-HIV-1 activity. Compounds 1-4 displayed anti-HIV-1 activity in a syncytial assay with EC(50) values of 12, 29.1, 34.2 and 5.3 microm, respectively, and thus exhibited potential therapeutic index (PTI) values of 56.7, 8.0, 1.6 and 7.0, respectively. All isolated compounds demonstrated a lack of cytotoxicity against the KB and BC-1 cancer cell lines.

Rhinacanthin-M, -N and -Q, natural products isolated from the medicinal plant Rhinacanthus nasutus, and 39 novel naphthoquinone esters have been synthesized in excellent yield by esterification of naphthoquinone-3-(propan-3'-ols) with benzoic or naphthoic acids. Almost all the naphthoquinone esters that contain a C-3 hydroxy group showed significant cytotoxicities against KB, HeLa, and HepG2 cell lines. In contrast, ester derivatives lacking the C-3 hydroxy group were inactive to the cancer cell lines. Two methyl substituents on the C-2' of propyl chain conferred more potent cytotoxicity than when there is only one or no methyl group. Naphthoate esters exhibited greater cytotoxicity than benzoate esters. Computer modeling has been done to obtain a first look at the mode of action in connection with these observations.

Physiological regulation of laccase production from Ganoderma sp. KU-Alk4, isolated in Thailand, was controlled by the initial glucose concentration in liquid culture. Different laccase isozymes were produced using different starting concentrations of glucose. With 1% glucose, two isozymes, KULac 1 and 2 were produced, while with 4% glucose, three different isozymes, KULac 3, 4 and 5, were produced. The KULacs differed in their molecular mass, ranging from 53 to 112 kDa. KULac 2 was a new laccase that had a different N-terminal amino acid sequence from other laccases previously reported. All the isozymes had optimum pH at 3.5 and were stable over the wide range of pH, 3.0-10.0, especially in alkaline pH. It is noteworthy that the activities of the four KULacs with 2,6-dimethoxyphenol were extremely high up to 90°C. They retained 100% of their activities at 60°C for 1 h.

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Cervical cancer is one of the most commonly diagnosed cancers in woman worldwide and is the first leading cause of cancer-related deaths in Thai women.1) The major cause of mortality associated with this disease is the metastasis of cancer cells that fails to respond to chemotherapeutic drugs. 2)Novel preventive and therapeutic strategies are therefore urgently needed to decrease the mortality associated with this malignancy.Natural products have been found to be a potential source of novel anticancer drugs over the decades and have much contributed to cancer chemotherapy such as etoposide, camptothecin, paclitaxel, etc. 3) In addition, these chemotherapeutic agents have been reported to exert their antitumor effects by inducing apoptosis. 4) Thus, chemical agents with strong apoptosis-inducing activity but minimal toxicity would be expected to have a potential utility as anticancer drugs.Rhinacanthone (3,4-dihydro-3,3-dimethyl-2H-naphthol-[1,2-b]pyran-5,6-dione), one of the main bioactive naphthoquinones, was isolated from Rhinacanthus nasutus which traditionally used in Thai folk medicine for treating various cancers including cervical and hepatocellular cancers. It has also been reported to have antiproliferative activity in various cancer cells 5,6) and antitumor activity against Dalton's lymphoma in mice.7) It has chemical structure closely related to b -lapachone (3,4-dihydro-2,2-dimethyl-2H-naphthol[1,2-b]pyran-5,6-dione) which was proved to be a novel anticancer drug and DNA topoisomerase I and II inhibitor. 8-11)Recently, we reported that rhinacanthins (C, N and Q), another naphthoquinones isolated from the Rhinacanthus plant, exhibited antiproliferative activity in various cancer cells 5) and induced apoptosis in human cervical carcinoma (HeLaS3) cells involving in G 2 /M cell cycle arrest and activation of caspase-3. 12) Rhinacanthins-N and -Q also act as topoisomerase II inhibitors.13) Therefore, it is possible that rhinacanthone functions on cancer cells by the same action as b-lapachone and/or rhinacanthins. Up to present, the potential anticancer mechanism(s) of this drug has not been elucidated. In present study, effects of rhinacanthone on the induction of apoptosis and its molecular mechanism in human cervical carcinoma (HeLa) cells were investigated. Here, we demonstrate that rhinacanthone, 1,2-naphthoquinone, induces apoptosis on human cervical carcinoma cells. To the best of our knowledge, this is the first report showing that rhinacanthone-induced apoptotic cell death is mediated via mitochondria-dependent pathway. Rhinacanthone would be a candidate for apoptosis-inducing cancer Rhinacanthone, a main bioactive naphthoquinone, isolated from roots of Rhinacanthus nasutus KURZ, (family Acanthaceae), a Thai traditional medicine, has been reported to possess anticancer effects, although the anticancer mechanism is still unclear. Therefore, we investigated the effects of rhinacanthone on cell proliferation, cell cycle progression and apoptosis induction in human cervical carcinoma ( The apoptot...