Secondary metabolites and biological activities of oils and oilseeds from three species: Lannea microcarpa Engl. and K. Krause (Anacardiaceae), Sclerocaria birrea (A. Rich) Hochst (Anacardiaceae), and Pentadesma butyracea Sabine (Clusiaceae). Master thesis. Université de Ouagadougou.

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Ethnobotanical studies and analysis of composition and physico-chemical properties of oils, led by QualiTree project on wild oilseed plants of southwestern Burkina Faso, have revealed that many species have high potential (quantitative and qualitative) oils with food, cosmetic, medicinal and fat stabilizing properties.

To determine the molecular principles responsible for these interesting properties, the seed extracts of the three most active species (Lannea microcarpa, Sclerocarya birrea and Pentadesma butyracea) were investigated for phytochemicals and in vitro biological activity.

For this purpose, standard laboratory methods for extraction, phytochemical screening (Ciulei colorimetric test) , spectrometric dosages (phenolics, flavonoids), thin layer chromatography (TLC), assessment of antiradical and antioxidant activities (DPPH and FRAP methods), as well as test for fat stabilizing power (Rancimat test on Shea butter) of different extracts were determined.

The results of extraction were quite interesting, as well as with non-polar solvents and with polar solvents.

Phytochemical screenings to identify major phytochemical groups present in the extracts, allowed to show the presence of phenolic compounds, coumarins, flavonoids, sterols, triterpenoids, saponins.and carotenoids.

Quantitative determination of phenolic compounds showed that the amounts of total phenolics and total flavonoids in various extracts depend on the solvent nature; with high level in the polar extracts: for example we obtained with the aqueous extract, 33. 43 ±0. 43; 30. 77 ±0. 53; 351. 60 ±1. 40 mg of equivalent gallic acid/g of seed powder, respectively for Lannea microcarpa, Sclerocarya birrea and Pentadesma butyracea).

Thin layer chromatography (TLC) analysis allowed the detection of many minor secondary metabolites like carotenoids and Tocopherols.

Evaluating the anti-radical activity (DPPH) of extracts, we found very good activities. Thus, the ethanol extract of Lannea microcarpa gave an IC50 of 1.44 microgram / ​​ml.

Testing the antioxidant activity (FRAP method), it was showed that the extracts rich in polyphenols were the most active. Thus, the methanol extract of P. butyracea gives a very good activity of 213 mg ascorbic acid equivalent/g.

These results led to a good activity for the stabilization of Shea butter, using the Rancimat test. We obtained an increase in the Rancimat induction time, with many extracts. For example the chloroform extract from seeds of Lannea microcarpa gave a Rancimat induction time of 3.75 hours, corresponding to an improvement of 91.47% as compared to the control.

These high levels of interesting phytochemicals in the seed extracts may justify the properties of the oils. Further studies to elucidate these secondary metabolites, particularly the minor compounds would be able to precise the industrial uses, and also fingerprints for fighting against eventual fraud or adulteration on the oils produced from these species.

Keywords: seed oil, secondary metabolites, bioactive oil, oil thermostability, QualiTree, Burkina Faso.