Flavonoid Versus Artemisinin Anti-malarial Activity in Artemisia annua Whole-Leaf Extracts

Abstract

Artemisinin, a sesquiterpene lactone produced by Artemisia annua glandular secretory trichomes, is the active ingredient in the most effective treatment for uncomplicated malaria caused by Plasmodium falciparum parasites. Other metabolites in A. annua or related species, particularly flavonoids, have been proposed to either act as antimalarials on their own or act synergistically with artemisinin to enhance antimalarial activity. We identified a mutation that disrupts the CHALCONE ISOMERASE 1 (CHI1) enzyme that is responsible for the second committed step of flavonoid biosynthesis. Detailed metabolite profiling revealed that chi1-1 lacks all major flavonoids but produces wild-type artemisinin levels, making this mutant a useful tool to test the antiplasmodial effects of flavonoids. We used whole-leaf extracts from chi1-1 and mutant lines impaired in artemisinin production in bioactivity in vitro assays against intraerythrocytic P. falciparum Dd2. We found that chi1-1 extracts did not differ from wild-type extracts in antiplasmodial efficacy nor initial rate of cytocidal action. Furthermore, extracts from the A. annua cyp71av1-1 mutant and RNAi lines impaired in amorpha-4,11-diene synthase gene expression, which are both severely compromised in artemisinin biosynthesis but unaffected in flavonoid metabolism, showed very low or no antiplasmodial activity. These results demonstrate that in vitro bioactivity against P. falciparum of flavonoids is negligible when compared to that of artemisinin.

In vitro analyses of Artemisia extracts on Plasmodium falciparum suggest a complex antimalarial effect

“…This finding is consistent with the relative difference in ART content and suggests that the in-vitro antimalarial potential of both Artemisia species was largely dependent upon ART content. A recent report corroborates the results of our study [ 34 ]. They used a different approach whereby they used an A .…”

“…leaves for parasite treatment, e.g. hot water [20,31–34, this study] chloroform:ethanol [ 34 ], chloroform [ 33 ], dichloromethane (this study); method of parasite measurement, microscopic counting [ 32 – 34 ], lactate dehydrogenase [ 31 , 33 ] vs. SYBR Green assay [20,33,35, this study], etc. Unless such variables are fully controlled, the validity of any conclusion is challenging.…”

“…Recently, Czechowski et al . (2019) [ 34 ] used an A . annua mutant with normal levels of flavonoids that produces no ART to challenge P .…”

In-vitro analysis of free radical scavenging activities and suppression of LPS-induced ROS production in macrophage cells by Solanum sisymbriifolium extracts

“…Medicinal plants, which are the basis of traditional medicine in various countries, have been investigated for their pharmacological properties and have revealed numerous significant novel phytochemicals with the potential to treat and manage diseases 10 . This includes the discovery of paclitaxel (Taxol), an anticancer drug discovered from the bark of the Himalayan Yew tree 11 ; berberine isoquinoline alkaloid an antineoplastic, antidiabetic drug found in plants belonging to Berberidaceae family 12 , and Artemisinin, an antimalaria drug derived from Artemisia annua 13 , to mention a few. In recent studies, plants and their constituents have shown significant potential as therapeutic agents for oxidative stress and include polyphenolic compounds such as resveratrol, gallic acid, catechin, quercetin, kaempferol, and several anthocyanins from grapes skin 14 .…”

Characterization of Malaria Preventive Extracts from Myrsine africana Seeds

“…Similar findings were observed by Falodun et al [36] whereby the methanolic extracts gave the best anti-plasmodial activity. Alongside DMSO and chloroform solvents, methanol have over a long period been used in extraction of various anti-plasmodial compounds from plants [37]. Fig.…”