Quantification of Artemisinin in flowers and leaves of Cultivars and Wildlings of Artemisia Annua l. in western Kenyan soils
Odundo, Joseph Ochieng’
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Malaria claims about 1.5million lives around the world annually with over 90% of the cases and deaths occurring in sub-saharan Africa. Malaria is caused by the parasite Plasmodium falciparum which is transmitted by the female anopheles mosquito. The parasite has since developed resistance to conventional treatments such as chloroquine and the combination sulphadoxine/pyrimethamine. This has made it difficult to fight malaria specifically in sub-saharan region. World Health Organization thus recommends the use of Artemisinin-based combination therapy (ACT) which is an effective drug based on artemisinin, a sesquiterpene lactone peroxide found in the plant Artemisia annua L. The government of Kenya allocates substantial amounts in its annual budget for the importation of ACTs to fight the parasite while clones of A. annua have since been developed and introduced in Kenya since 1990s. The flowers and leaves of the plant have numerous medicinal and environmental benefits, one of which is being a natural herbicide and in essence a mosquito repellant. The plant can either be field-grown (cultivars) or grows naturally (wildlings). The commercially viable levels of artemisinin in A. annua are above 0.6% although this percentage may vary depending on the levels of Nitrate ion (NO3-), Ammonium ion (NH4+), Zinc (Z) and Boron (B) in the soil. In Kenya, A. annua anamed (A3), a clone of A. annua is commercially cultivated by farmers in parts of Central and Rift-valley provinces and it gives an assay in the range of 0.8-1.2% dry matter (DM) artemisinin content and covers an area of approximately 10,000ha. On the other hand, its cultivation has not been fully embraced in the western region (Western and Nyanza provinces) where malaria prevalence levels are above 40%. This study therefore determined the levels of artemisinin in flowers and leaves of both cultivars and wildlings of A3 in western region. The levels of Zn, B, NH4+ and NO3- in the soils were also determined at two depths. The samples were collected from Kajulu, Nyakach, Maseno and Asembo in Kisumu county and Ingidi in Vihiga county. The methods of analysis were Reversed Phase-High Performance Liquid Chromatography for artemisinin, Flame Atomic Absorption Spectrometry for Zn & B and Ion Selective Electrode for NO3- and NH4+ ions. The mean levels of artemisinin in cultivars ranged from 0.12-1.17%DM in flowers and 0.04-0.88%DM for leaves while in wildlings it ranged from 0.02-0.24%DM in flowers and 0.08-0.01%DM. Viable levels were recorded for flowers of cultivars at Ingidi (1.17±0.02%DM), Maseno (0.85±0.02%DM) and Kajulu (0.72±0.02%DM). Nyakach recorded viable levels in the leaves of cultivars (0.88±0.02%DM) and leaves of wildlings (0.90±0.02%DM). The mean levels obtained for soil samples were 49.13±0.42-117.20±1.39μg/g Zn, 0.00-587.33±41.00μg/g B, 0.02±0.00-0.47±0.00μg/ml NH4+ and 0.27±0.01-1.45±0.01μg/ml NO3-. The results of this study have shown that A. annua grown in western region contain commercially viable levels of artemisinin in cultivars. These levels can be improved if Zn and B levels are controlled and the nitrate to ammonium ions ratios optimized in the range 2-5 in the soil where the plant grows. Therefore it would be recommended that residents of this region be encouraged to cultivate A. annua in large scale and appropriate soil management practices be employed to maximize the artemisinin yields for improved management of malaria and the parasite.