Seeds of two selected clones of Artemisia annua L., TC1 and TC2, were germinated in a greenhouse. Four-week-old seedlings from both clones were grown in the Thù Ðúc province of Ho Chi Minh City on 2nd January 2009 and Ðà Lat on 20 th January 2009. During this study period in Thù Ðúc province, which is situated 4–5 m above sea level, was experiencing a tropical, dry season with temperatures ranging from 26.2°C–32.8°C. Ðà Lat, situated at 1500–2000 m above sea level, was having temperate, dry season with lower temperatures, ranging from 10.5°C–18.0°C. The high temperatures and low elevation in Thù Ðúc Province led to slow vegetative growth for all of the plants from the two different clones and the artemisinin contents were significantly reduced. The temperate environment of Ðà Lat supported robustly growing plants, with plant heights and branch lengths 4–5 times taller and longer that those planted at Thù Ðúc Province. The artemisinin contents of A. annua planted at Ðà Lat were 3–4 times greater than those cultivated at Thù Ðúc Province. Hence, this study indicated that the variations observed in plant growth and artemisinin contents were due to temperature effects because the two selected clones were genetically homogenous. The cold weather of Ðà Lat was suitable for planting of A. annua as opposed to the tropical weather of Thù Ðúc Province.
This study focuses on the larvicidal, oviposition, and ovicidal effects of a crude extract of Artemisia annua against Aedes aegypti, Anopheles sinensis, and Culex quinquefasciatus. Dried cells of Artemisia annua from cell suspension cultures were extracted using hexane. The extract showed moderate larvicidal effects against mosquitoes. At 24-h post treatment, the LC50 values for Anopheles sinensis, Aedes aegypti, and Culex quinquefasciatus were recorded as 244.55, 276.14, and 374.99 ppm, respectively. The percentage mortality of larvae was directly proportional to the tested concentration. Anopheles sinensis was found to be the most susceptible species, whereas Culex quinquefasciatus was the most tolerant to the Artemisia annua extract. The results indicated that the Artemisia annua extract showed concentration-dependent oviposition deterrent activity and had a strong deterrent effect. At 500 ppm, the percentage effective repellency was more than 85% compared with the control group for all the species, with oviposition activity index values of -0.94, -0.95, and -0.78 for Aedes aegypti, Anopheles sinensis, and Culex quinquefasciatus, respectively. In the ovicidal assay, the percentage hatchability of eggs after treatment with 500 ppm of Artemisia annua extract was significantly lower than the control, with values of 48.84 ± 4.08, 38.42 ± 3.67, and 79.35 ± 2.09% for Aedes aegypti, Anopheles sinensis, and Culex quinquefasciatus, respectively. Artemisia annua was found to be more effective against Aedes aegypti and Anopheles sinensis compared with Culex quinquefasciatus. This study indicated that crude extract of A. annua could be a potential alternative for use in vector management programs.
Artemisia annua L., a medicinal herb, produces secondary metabolites with antimicrobial property. In Malaysia due to the tropical hot climate, A. annua could not be planted for production of artemisinin, the main bioactive compound. In this study, the leaves of three in vitro A. annua L. clones were, extracted and two bioactive compounds, artemisinin and a precursor, were isolated by thin layer chromatography. These compounds were found to be effective in inhibiting the growth of Gram-positive and Gram-negative bacteria but not Candida albicans. Their antimicrobial activity was similar to that of antibactericidal antibiotic streptomycin. They were found to inhibit the growth of the tested microbes at the minimum inhibition concentration of 0.09 mg/mL, and toxicity test using brine shrimp showed that even the low concentration of 0.09 mg/mL was very lethal towards the brine shrimps with 100% mortality rate. This study hence indicated that in vitro cultured plantlets of A. annua can be used as the alternative method for production of artemisinin and its precursor with antimicrobial activities.