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Aims@#This study aimed to evaluate the antimicrobial activity of naturally derived phenylpropanoids from Alpinia conchigera (A. conchigera) Griff. and its synthetic analogues, as well as interactions between selected compounds with first-line tuberculosis (TB) drug, rifampicin, against Mycobacterium smegmatis, a potential opportunistic nontuberculous mycobacterium (NTM) and a surrogate organism for TB. @*Methodology and results@#Twelve phenylpropanoids of A. conchigera were evaluated for antimicrobial activity against M. smegmatis (ATCC 14468). The phenylpropanoid compound from A. conchigera with the lowest minimum inhibitory concentration and bactericidal (MIC, MBC) values were selected for checkerboard tetrazolium microplate assay (TEMA) with rifampicin to determine drug interactions. A majority of the compounds had antimicrobial activity, however, purified natural compound 1'S-1'-acetoxychavicol acetate (ACA) showed the highest antimicrobial activity with an MIC value of 62.5 µg/mL against M. smegmatis. The combination of ACA and rifampicin produced indifferent interaction with fractional inhibition concentration (FIC) index of 1.5, while the combination of rifampicin and ACA synthetic analogue 4-allyl-2,6- methoxyphenyl isobutyrate produced a synergistic interaction effect with FIC index of 0.5. None of the compounds tested were bactericidal but appear to be bacteriostatic.@*Conclusion, significance and impact of study@#This study presents the first report on the antimicrobial potential of natural A. conchigera-derived ACA against M. smegmatis as well as the synergistic interaction of 4-allyl-2,6- methoxyphenyl isobutyrate with rifampicin which warrants further investigation.

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Laboratory bioassays on insecticidal activity of hexane crude extract derived from four species of Zingiber: Zingiber officinale var. rubrum (HZOR), Zingiber montanum (HZM), Zingiber spectabile (HZS) and Zingiber zerumbet (HZZ) were carried out against three mosquito larvae vector: Ae. albopictus, Ae. aegypti, and Cx. quinquefasciatus. GC/MS analysis revealed 43, 82, 50, and 51 compounds from HZO, HZM, HZS, and HZZ, respectively. The major principal constituents found in HZO extract were zingerone (14.92%) and benzaldehyde dimethyl thiol acetal (11.61%); HZM extract were dimethyl 4-methylphthalate (12.64%) and carbendazim (12.62%); HZS extract had 1,1'-ethylenebisdecalin (42.52%) and 1- pentadecyne (11.5%); and HZZ extract were humulene epoxide II (20.84%) and zerumbone (60.4%). Assessment of larvicidal efficacy demonstrated good larvicide effects towards all the crude hexanes. The mortality was observed after 24h exposure. The highest larvicidal mortality of Ae. albopictus larvae was found in HZOR, HZM, and HZS (LC50= 96.86, 99.04 and 93.35 mg/L; LC90= 168.65, 153.77, and 168.65 mg/L) respectively. HZM and HZZ were effective against Ae. aegypti larvae with LC50= 84.95 and 82.05 mg/L and LC90= 134.85 and 121.05 mg/ L, respectively. HZZ showed the most effective extract against Cx. quinquefasciatus larvae with LC50= 49.28 mg/L and LC90= 83.87 mg/L. No mortality was recorded in the control. Results from studies suggest that bioassay-guided effective extracts of Z. officinale var. rubrum, Z. montanum, Z. spectabile and Z. zerumbet are potential larvicidal candidates for controlling Ae. albopictus, Ae. aegypti, and Cx. quinquefasciatus.

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A phytochemical study of Alphonsea cylindrica King (unreported) has led to the isolation of six alkaloids. The compounds were identified as kinabaline (1; azafluorenone alkaloid), muniranine (2), O-methylmoschatoline (3; oxoaporphine alkaloid), lysicamine (4), atherospermidine (5) and N-methylouregidione (6; 4, 5-dioxoaporphine alkaloid). The structures of the isolated compounds were determined based on the spectroscopic techniques and by comparison with data reported in the literature. Alkaloid 2 was isolated as a new derivative of azafluorenone while alkaloids 1, 3 - 6 were isolated for the first time from Alphonsea species. In addition, alkaloid 3 and 4 showed inhibition zone against Staphylococcus aureus, Pseudomonas aeruginosa and Bacillus cereus in disc diffusion test. The minimum inhibition concentration (MIC) values of lysicamine (4) against S. aureus, B. cereus and P. aeruginosa were found to be smaller than O-methylmoschatoline (3). Therefore, the reported antibacterial activity showed the potential of this plant as natural antibacterial agent and supported the documented traditional use of Alphonsea sp. in the treatment of diarrhea and fever.

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OBJECTIVE@#To study antiplasmodial and antioxidant activities of the isolation of alkaloids from the active dichloromethane extract of Alseodaphne corneri.@*METHODS@#Phytochemical studies of the crude extract led to the isolation of six alkaloids using recycle high performance liquid chromatography and preparative thin layer chromatography. The antiplasmodial activity of the isolated compounds was evaluated using the histidine-rich protein II assay. The isolated alkaloids were also tested for their antioxidant activity using three different assays; DPPH, ferric reducing ability of plasma and metal chelating assays.@*RESULTS@#Malaria infection caused the formation of free radicals which subsequently led to oxidative stress and apoptosis. The antioxidant properties of the alkaloids under investigation revealed that in addition to the antiplasmodial activity, the alkaloids could also prevent oxidative stress. (+)-laurotetanine and (+)-norstephasubine exhibited strong antiplasmodial activities with IC50 values of 0.189 and 0.116 μM, respectively.@*CONCLUSIONS@#Interestingly, the two most potent compounds that exhibit antiplasmodial activity also exhibit good antioxidant activities. The crude dichloromethane extract and the isolated compounds exert substantial antiplasmodial and antioxidative activities which in turn suppress oxidative stress and cause less damage to the host.

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Objective: To study antiplasmodial and antioxidant activities of the isolation of alkaloids from the active dichloromethane extract of Alseodaphne corneri. Methods: Phytochemical studies of the crude extract led to the isolation of six alkaloids using recycle high performance liquid chromatography and preparative thin layer chromatography. The antiplasmodial activity of the isolated compounds was evaluated using the histidine-rich protein II assay. The isolated alkaloids were also tested for their antioxidant activity using three different assays; DPPH, ferric reducing ability of plasma and metal chelating assays. Results: Malaria infection caused the formation of free radicals which subsequently led to oxidative stress and apoptosis. The antioxidant properties of the alkaloids under investigation revealed that in addition to the antiplasmodial activity, the alkaloids could also prevent oxidative stress. (+)-laurotetanine and (+)-norstephasubine exhibited strong antiplasmodial activities with IC