Download presentation
Presentation is loading. Please wait.
Published byMarcia Barton Modified over 9 years ago
1
The potential of plants as a source of anti-malarial agents Dr Geoffrey M. Rukunga Kenya Medical Research Institute PO BOX 54840 NAIROBI E-mail
2
Global statistics of Malaria 1.5 – 2.7 million deaths annually Over 1 billion clinical episodes 300 – 500 million people infected Every 10 – 30 seconds a child dies of malaria
3
Impact of malaria in Africa Major health problem in the tropics About 90 million clinical cases annually. Malaria leads to economic loss. Most affected are pregnant women and children Under 5 years.
4
What contributes to the problem? Resistance to conventional drugs. Affordability of available drugs. There for need to continue searching for new agents
5
Plant drugs Approximately 80% of the people in the developing countries depend on traditional medicine. The discovery of quinine and artemisinin has stimulated interest in medicinal plants as sources of new antimalarial drugs.
6
Selection of plants for antimalarial activity Ethno medical bases Random selection
7
Methodologies Extractions – water or organic solvent In vitro assays – IC 50s Cytotoxicity assays CC50’s Selectivity index (S.I) = IC 50/CC50 In vivo assays – percentage chemosuppression of parasitaemia. Toxicity in animals. Activity guided isolation of the active compound (?)
8
So many publications yet few candidates anti-malarial agents Anti-malarial compounds rare. Most studies ends up with only in vitro assays. If beyond in vitro assay – then toxicity - problem Usually because of lack of resources - trained personnel - equipment - Finances
9
Categorization of plants extracts with in vitro anti-plasmodial activity Category 1: High activity IC 50 equal or less than 10 g/mL Category 2: Moderate activity IC 50 between 10 and 100 g/mL Category 3: Low or no activity IC 50 Above 100 g/mL
10
Category 1 (High activities) 120 plant extracts from 74 plant species, belonging to 34 families. Some of the families with more species than others: Annonaceae (alkaloids) Apocynaceae (Alkaloids) Asteracea (sesquiterpenes) Celestraceae (Triterpenes) Meliaceae (limonoids) Simaroubaceae (quassinoids) Menispermaceae (Alkaloids) Rutaceae (Alkaloids) Rubiaceae (alkaloids)
11
Category 2 – moderate activities 203 plant extracts from 129 plant species, belonging to 50 families. Some of the families with more species than others: Annonaceae Asteraceae Meliaceae Loganiacea Fabaceae
12
Classes of compounds with high anti-malarial activities Alkaloids Basic compounds -highly bioactive compounds. The structures are very diverse Families containing the compounds includes AnnonaceaeLoganiaceae MenispermaceaeAsclepiadaceae Dioncophyllaceae Rubiacea Rutaceae Apocynaceae
13
Quinine – An alkaloidal compound
14
Quassinoids Heavily oxygenated lactones majority with C-20 basic skeleton. The structures are very diverse Simaroubaceae – is the family associated with quassinoids
15
A quassinoid from Simaba guianensis (Simaroubaceae) IC 50 < 1.7 ng/mL
16
Sesquiterpenes Biosynthetically made from three 5-carbon isoprene units skeleton Among the most active terpenoids Artemisinin belongs to thisd class of compounds. Families identified with highly active sesquiterpenes includes AsteraceaeSiparunaceae CyperaceaeValerianaceae Rosaceae
17
Artemisinin and Mustakone
18
Triterpenes Triterpenes. Biosynthetically made from 6 units isoprene units Diverse sructures. Some triterpenes have exhibited high anti-plasmodial activity. Families associated includes: -Ancistrocladaceae - Meliaceae - Simaroubaceae - Celestraceae
19
pristimerin – triterpene from Maytenus senegalensis - Celestraceae IC 50 < 200 ng/mL
20
Limonoids Tetranoterpenoids a class of compounds highly active. IC 50s < 1ug/mL Family associated with these compounds – Meliaceae
21
Discussions Points to consider in the categorization of the plant extracts with anti-plasmodial activity. Type of extract Strain of Plasmodium parasite used in the assay Part of the plant extracted Geographical location of plant Time of the year harvested Thus categorization is a guide
22
Way forward Prioritization of plants as source of anti-malarial agents. Families whose exts have high anti-malarial activity (cat 1&2). Families that contain class of compounds with known potent anti-malarial activity e.g liminoids, alkaloids, quassinoids etc. Cytotoxicity after in vitro anti-plasmodial assays. Confirm activity in vivo Toxicity studies in animals. plant part: leaves > stems > roots Ease of propagation, cultivation etc Team work – the only answer.
23
End Thank you
Similar presentations
© 2025 SlidePlayer.com. Inc.
All rights reserved.