The species S. gabonensis Warb. has been the subject of some chemical investigations. The essential oils of S. gabonensis Warb were obtained from seeds and bark by hydrodisillation. Analyses by GC and GC/MS indicate a sesquiterpenes, germacrene D (35%) and β-caryophyllene (12%) in the seed oil while trans-α-bergamotene (39.5%) and β-caryophyllene (13%) are the major components of the bark oil. These volatile extracts did not reveal important antioxidant and antiradical activities (Agnaniet et al., 2004).

The stem bark and seeds of Staudtia kamerunensis Warb is being investigated for the first time. The seed hexane extract is composed mainly of glycerol tetradecanoate (trimyristin, glycerol trimyristate) and six lignans: otaobain, hydroxyotobain, otobaphenol, licarinA, licarin B and (-) dihydroxyguaiaretic acid were isolated. The ethyl acetate extract of the stem bark gave a seventh lignan, otobuiene (Yankep, 1999). A few years earlier, a diterpene acid (staudtienic acid) was isolated and identified in the specie S. kamerunensis (Noumbissie, 1992).

Secondary metabolites extracted from oilseeds of S. kamerunensis var. gabonensis could have a wide range of applications. Fatty acids play an essential role in several processes such as platelet aggregation, inflammation, immunity, etc. (Leclerf, 2011). Today, antioxidants from natural products such as plants, fruits and seeds are widely sought and used in several fields such as dietetics, agri-food, cosmetology and the medical field. It is known that polyphenolic compounds have interesting properties for the human body, both nutritionally and medically (Charrouf and Guillaume, 2007a).

In humans, oxidative damage to DNA, lipids and proteins is associated with certain chronic diseases such as cardiovascular diseases, certain cancers, diabetes, inflammatory diseases, Alzheimer's disease and other neurodegenerative diseases, as well as the aging process (Choi et al., 2018; Klaunig, 2018; Luc et al., 2019; Tönnies and Trushina, 2017; Kozakiewicz et al., 2019). An antioxidant or molecules isolated from the oilseed extracts of S. kamerunensis var. gabonensis could, for example, help prevent the appearance of these pathologies.

The results of our investigations relate to the polar and apolar extracts of the oilseeds of S. kamerunensis var. gabonensis in order to carry out phytochemical tests and evaluate their antiradical activity for their potential use in biotechnological fields such as  agri-food,  cosmetics  and pharmacology.

Purchase of chemicals

ABTS (2,2'-Azinobis [3-ethylbenzothiazoline-6-sulfonic acid]), gallic acid, potassium persulfate (K2S2O8) and hydrated sodium dihydrogen phosphate were purchased from Sigma-Adrilch (Saint -Quentin Fallavier, France). All these products were required for analysis. Concentrated H2SO4 (sulfuric acid) (95-97%), cyclohexane, trichlorethylene, acetone, absolute ethanol, chloroform, isoamyl alcohol, iron perchloride, magnesium shavings, chloroform, hydrochloric acid, acetic anhydre, Fehling's liquor, Dragendorf's reagent were also purchased from Sigma-Aldrich, Carlo Erba or Prolabo and used without further purification. Distilled water was obtained from Chimie Gabon. Molish's reagent, solutions of 1% iron perchloride, 2% ferric chloride, 1% sodium hydroxide, 10 and 25% ammoniac in water and hydrochloric alcohol were prepared in the laboratory from reagents and grade chemicals using procedures in the literature.

Plant material

The seeds of S. kamerunensis var. gabonensis (Myristicaceae) were collected in January 2021 from Sibang Herbarium of Pharmacopoeia and Traditional Medicine Institute (IPHAMETRA), Libreville, Gabon and then sent to the Laboratory of IPHAMETRA where they were dried in the sun for several days.

Extraction method by maceration

Preparation of samples of S. kamerunensis var. gabonensis for the trials began with the fragmentation and crushing of oilseeds. The seeds were first broken with a hammer to facilitate grinding. The seed fragments are then introduced in small quantities, in turns, into a Retsch-type grinder with IPHAMETRA. This approach is necessary to obtain a particle size corresponding to the requirements of ASTM standard No. 1105 (1996) in terms of particle size to quantify the extract rate. The powder collected was sieved to a diameter of less than 2 mm and kept in an oven at 40°C until the time of the tests.

In order to extract all the molecules of interest (polar and apolar), a sequential extraction by maceration using solvents of increasing polarity (cyclohexane, trichlorethylene, acetone, ethanol, distilled water) was carried out taking into account its efficiency in extracting and preserving the molecules of interest. This technique is similar to infusion and is done at room temperature. It is generally used for heat-sensitive compounds.

80 g of S. kamerunensis var. gabonensis were introduced into a 500-mL glass Erlenmeyer flask containing 400 mL of cyclohexane in order to collect lipid and apolar molecules or eliminate compounds such as oils, fats, sterols. The Erlenmeyer flask is then closed with a rubber stopper covered with aluminum foil. The mixtures were subsequently stirred at room temperature on a PIERRON type stirrer for 24 h. Thereafter, the mixtures were separated by vacuum filtration with a Whatman No. 4 type filter in a Büchner type funnel. The retentate or the extraction cake remaining in the upper part of the filter was immediately put back into solution for a second extraction in 400 mL of trichlorethylene in order to still collect the lipid molecules not extracted by cyclohexane. A third, fourth and fifth extraction were carried out respectively in acetone, ethanol and finally water to extract the phenolic compounds and the polar  molecules  while  following  the  same  extraction steps as the cyclohexane solvent. After extraction, the organic solvent extracts (cyclohexane, trichlorethylene, acetone, ethanol) were evaporated in a pre-weighed flask using a rotary evaporator under vacuum. For aqueous extracts, freeze-drying will dry them completely. These five successive extractions were repeated on four samples (three evaporated samples for the calculations of the extractable levels and the anti-radical tests, one non-evaporated sample or filtrate for the phytochemical tests). The extracts with organic solvents were placed in an oven at 40°C until a constant mass was measured. All the extracts are stored in the refrigerator in closed bottles and covered with aluminum foil for the next tests. The percentage of extractables compared to the initial mass of seed powders of S. kamerunensis var. gabonensis used is determined using the following Equation (1):

Where: R: yield of extracts in %; Mext: mass of the extract after evaporation or freeze-drying in grammes; Mech: anhydrous mass of the seed powder sample in grammes.

Screening phytochimique

The reagent used to carry out the phytochemical screening of the extracts was prepared according to the protocols described by Houghton and Raman (1998), Akinjogunla et al. (2010) and Badiaga (2011). All the different tests were carried out in triplicate.

Test for alkaloids: 2 mL of extract was placed in a test tube and then a few drops of Dragendorff's reagent solution was added. The appearance of a red-orange precipitate indicated the presence of alkaloids as described by N’Guessan (2009).

Test for polyphenols: 2 mL of the extract was placed in a test tube, thereafter a few drops of the 2% ethanolic ferric chloride solution was added. The appearance of a blue-blackish colour indicated the presence of polyphenols according to N’Guessan (2009).

Test for sterols and triterpenes: This was determined by placing 1 mL of the acetic anhydride which is added to 2 mL of each extract. 1 mL of concentrated H₂SO₄ (sulfuric acid) is then poured into tubes (this is the reaction of Libermann-Buchard). The appearance of a purple colour and coloring of the supernatant blue or purple green indicates the presence of sterols or triterpenes respectively as described by Nze Kamsi et al., (2020).

Presence of tannins: This was determined by adding to 1 mL of extract, 1 mL of distilled water and 1 to 2 drops of FeCl₃ solution (Iron (III) chloride) diluted to 1%. The appearance of a dark green colour indicated the presence of tannins (Bentab Lasgaa, 2015 cited by Hamid, 2018).

Test for reducing compounds: 2 mL of extract was placed in a test tube, followed by 2 mL of Fehling's liquor. The whole content was then poured into a boiling water bath for 8 min. The appearance of a brick red precipitate indicated the presence of reducing compounds as reported by Bentab and Lasgaa (2015) cited by Hamid (2018). 

Test for flavonoids: 1 mL of extract was introduced into a test tube; thereafter 1 mL of hydrochloric acid was added, followed by 1 mL of isoamyl alcohol and then a few shavings of magnesium. The appearance of a pinkish-orange  colour  indicated  the  presence  of flavonoids as reported by Harborne and Grayer (1988).

Test for saponosides: These were identified by placing 10 mL of each extract in a test tube which was shaken vigorously with a vortex for 15 s. The tube was left to stand for 15 min; thereafter the appearance of persistent foam indicated the presence of saponins as reported by N’Guessan (2009).

Test for cardiac glycosides: 2 mL of chloroform was added to 1 mL of each extract. The appearance of a reddish-brown colour after adding a few drops of concentrate H2SO4 (sulfuric acid) indicated the presence of cardiac glycosides as reported by Yam et al. (2009).

Presence of free quinones: This was determined by adding a few drops of 1% NaOH (sodium hydroxide) to 1 mL of each extract. The appearance of a colour turning yellow red or purple indicated the presence of free quinones as reported by Oloyede (2005).

Test for anthraquinones: To 2 mL of each extract was added 1 mL of 10% NH4OH (ammoniac). After shaking, the appearance of a purple colour indicated a positive test according to Oloyede (2005).

Test for leucoanthocyanins: These were identified by adding to 5 mL of each extract, 5 mL of hydrochloric alcohol and then a few drops of isoamyl alcohol. The mixture was heated for two minutes in a boiling water bath. The appearance of a red coloration indicated the presence of leucoanthocyanins as reported by Fournet (1979).

Test for carotenoids: To each 2 mL of the extract, 0.5 mL of concentrated H2SO4 (sulfuric acid) is added. The appearance of a blue colour that turned red indicated the presence of carotenoids according to Ntsame Nze (2020).

Identification of mucilages: 1 mL of extract was introduced into a test tube followed by 5 mL of absolute alcohol. Obtaining a fluffy precipitate after shaking indicated the presence of mucilage as described by Awor et Samseny (2003) cited by Hamid (2018).

Determination of total sugars: To 1 g of each extract, 3 drops of Molish's reagent (for a volume of 100 mL, mix 0.25 g of 1-Naphthol + 50 mL of ethanol and 50 mL of 20% sulfuric acid) were added, followed by 1 mL of concentrated H2SO4  (sulfuric acid). The appearance of a purple interphase indicated their presence as reported by Feuya et al., (2015).

Test for coumarins: 1 mL of NH4OH (ammoniac) diluted to 25% was added in 2 mL of extract. The whole content was heated in a water bath for 5 min and then a UV reading was taken at 365 nm. The appearance of an intense fluorescence in the tube showing either yellow, blue, blue-green, orange, purplish pink indicated the presence of coumarins as described by Awor et Samseny (2003) cited by Hamid (2018).

Determination of free anthracene derivatives: This was obtained by adding 1 mL of NH4OH (ammoniac) diluted to 25% to a 1 mL of extract in a test tube. After stirring, the appearance of a more or less red colour indicated their presence as described by Awor et Samseny (2003) cited by Hamid (2018).

Anti-radical activity

The anti-free radical activity was determined by UV spectrophotometry using a V-200 spectrophotometer (BOECO, Germany). The optical density was read at 734 nm recording the maximum  absorption  wavelength  of  the  radical  cation ABTS • +. 

Preparation of "reference antioxidant" gallic acid solutions

Gallic acid (3,4,5-trihydroxybenzoic acid) is an aromatic organic compound, used as a reference anti-free radical compound. Ten working solutions, in decreasing concentrations, ranging from 0.94 to 0.094 µg/mL were prepared by diluting gallic acid in distilled water.

Preparation of seed solutions of S. kamerunensis var. gabonensis

Ten solutions of increasing concentrations ranging from 2.5 to 200 µg/mL of different S. kamerunensis var. gabonensis extracts were prepared by dissolving the powder in the extraction solvent.

Measurement of anti-radical activity

The principle of the test for measuring the anti-radical activity by the ABTS method was based on the decrease in the absorbance at 734 nm of the radical cation ABTS • + (blue-green colouration) in the presence of a potentially anti-radical compound which reduced the cation radical. The reduction in the radical form of ABTS • + led to a discolouration of the solution. The radical ion ABTS • + was obtained by reacting the ABTS molecule (7 mM) with potassium persulfate (2.45 mM) in distilled water for 16 h at room temperature and protected from light.

The ABTS • + solution obtained was diluted with sodium phosphate buffer (5 mM, pH = 7.4), in order to obtain a stock solution having an initial absorbance value at 734 nm between 0.65 and 0.70. The radical cation (ABTS • +) was stable for more than 2 days when stored at room temperature and protected from light. All the assays were carried out three times and the anti-free radical activity was calculated according to the following Equation (2):

Anti-free radical activity (%) = [1 - (Ar-Ab) / (Ai-Ab)] x 100             (2)

With Ar = remaining activity of ABTS • +, Ai = initial activity of ABTS • + and Ab = White activity. 

In fact, the reduction of the ABTS • + radical cation therefore amounted to determining the anti-free radical activity and in total, the antioxidant properties of S. kamerunensis var. gabonensis extracts compared to the antioxidant properties of gallic acid (standard). The anti-free radical activity was determined by UV spectrophotometry in cuvettes with an optical path of 1 cm (reaction volume of 2 mL). The incubation time was 6 min as reported by N’Negue et al. (2020).

Extraction yields

Results of the extractable contents of the oilseeds of S. kamerunensis var. gabonensis are presented in Table 1. These results indicate that the levels of extractables vary from one solvent to another. Cyclohexane extraction rates are the highest with 22.9%. The lowest yields of extracts are obtained with the solvents distilled water with 6.4%, trichlorethylene with 5.9%, ethanol with 4.8% and finally acetone with 4.6%. The overall extract levels of oilseeds of S. kamerunensis var. gabonensis are 44.6%.

The results of the phytochemical tests are presented in Table 2. The alkaloids were present in all the extracts (cyclohexane, trichlorethylene, acetone, ethanol and water). Polyphenols were abundant in polar extracts (acetone, ethanol and water) and absent in less polar extracts (cyclohexane, trichlorethylene).

The tannins were present in the ethanolic and aqueous extracts and absent in the other extracts (cyclohexane, trichloroethylene, acetone). Carotenoids were in low quantity in the cyclohexane and trichlorethylene extracts, moderately present in the acetone and ethanol extract, and absent in the aqueous extract. The flavonoids were present in the cyclohexane, acetone and aqueous extracts; they are moderately present in the trichloroethylene and ethanol extracts. Saponins were in very low quantity in the aqueous extract and absent in the rest of the extracts.

Anthraquinones were moderately present in the ethanolic and aqueous extracts, very low in the trichloroethylene and acetone extracts, and absent in the cyclohexane extract. Cardiac glycosides were weakly present in the cyclohexane, trichlorethylene, ethanol and water extracts, and absent in the ethanolic extract. Free quinones were present in the ethanolic and aqueous extracts, moderate in the acetone and trichlorethylene extracts, and very low in the cyclohexane extract. Mucilages were present in the cyclohexane extract and absent in the rest of the extracts.

Coumarins were weakly present in the cyclohexane extracts, aqueous, medium in the ethanolic extract and absent in the trichlorethylene and acetone extracts. Free anthracene derivatives  were  abundant  in  the  ethanolic extract and absent in the rest of the extracts. Leucoanthocyanins were absent in all extracts.

Phytochemical tests carried out on the seeds of S. kamerunensis var. gabonensis revealed the presence of alkaloids, tannins, polyphenols, reducing compounds, free anthracene derivatives, anthraquinones, total sugars, coumarins, free quinones, sterols and triterpenes, carotenoids, flavonoids, mucilages and traces of cardiac glycosides and saponins. These compounds have multiple therapeutic properties in the literature. Indeed, several authors have demonstrated that the consumption of foods rich in polyphenols reduces the development of much pathology, such as cancer, vascular diseases, hypertension, astrosclerosis (Hertog et al., 1993; Middleton et al., 2000; Leong and Shui, 2002).

The seeds of S. kamerunensis var. gabonensis contain a high proportion of alkaloids in the five extracts, but these compounds could involve interesting biological activities. Alkaloids have several pharmaceutical applications in humans, as these applications have been clinically proven (Mc Calley, 2002; Silvestrini et al., 2002). Alkaloids are researched for their physiological effects and their pharmacological activities which are exerted in various fields. They also act as antibiotics (Badiaga, 2012). Sterols and triterpenes are demonstrated in extracts of S. kamerunensis var. gabonensis or these compounds are recognized to have anti-inflammatory, antidiabetic, anticancer, antidiarrheal, antiviral and anti-HIV activities (Raman et al., 2012). We note the absence of leucoanthocyanins in our extracts, where the only flavoinoides present are free flavonoids. It is recognized that  flavonoids  have  antioxidant  and anti- inflammatory activities and play a positive role in the treatment of cardiovascular and neurodegenerative diseases (Wang et al., 2002). In some cases, they are known for their antiviral, antimicrobial and antitumor activity (Narayana et al., 2001; Seyoum et al., 2006).

A strong presence of tannins is marked in the ethanolic and aqueous extracts as these compounds exert an antidiarrheal, antiseptic, antibacterial and antifungal activity, as well as dermatitis (Aron and Kennedy, 2008). Tannins also have strong antioxidant activity. They are very good free radical scavengers. Phytochemical screening has detected the presence of coumarins which are known for their antioedematous properties in patients with advanced cancer: they are immunostimulants and would develop cytotoxic activity (Diallo, 2000). Traditionally, coumarin is used to facilitate urinary and digestive elimination functions. Mucilages are present in the cyclohexane extract of the seeds of S. kamerunensis var. gabonensis. Mucilages have confirmed functional and physical properties in the cosmetic fields (Chen et al., 2006). The commercial potential of mucilage in the pharmaceutical fields is based on its emollient and softening properties (Bemiller et al., 1993).

The carotenoids of the seeds of S. kamerunensis var. gabonensis could have potential for a pro-vitamin A activity. Vitamin A indeed participates in the maintenance of good vision and in the prevention of diseases that could affect the eyes. Carotenoids are also known to be antioxidants. They have a potential protective effect on the prevention and progression of cancers, cardiovascular diseases and cataracts (Jaswir et al., 2011). The carotenoids contained in these seeds could also be used as additives in the food industry as food coloring or in cosmetic products (Swiss Confederation, 2017; Jaswir et al., 2011).

Anthraquinone, free quinones and its natural derivatives are evidenced in the seeds of S. kamerunensis var. gabonensis. These compounds have proven therapeutic power to treat all functional intestinal disorders such as functional colopathy, laxophobia or constipation (Müller-Lissner, 1993). Some quinones have antioxidant, bronchial antispasmodic properties (Bruneton, 1997). Anthracene derivatives are responsible for laxative activity (Bruneton, 1987). Anthracene glycosides described as antidepressants are said to have antimicrobial properties (Cronquista, 1981).

In summary, the phytochemical screening of S. kamerunensis var. gabonensis reveals potential pharmacological, cosmetic and food-processing activities by the presence of numerous chemical families. By correlating the properties of the identified classes of secondary metabolites mentioned above, oilseeds of S. kamerunensi var. gabonensis constitute a target of choice and research work in the fields of biotechnology.

It is worth noting that phytochemical tests on seeds or barks of the species S. kamerunensis var. gabonensis have not been included in the literature to corroborate our results.

Anti-radical activity

Anti-free radical activity of gallic acid depending on the concentration

The anti-radical activity of the standard antioxidant "gallic acid" increased linearly with its concentration (Figure 1). The value of the IC50 which is the concentration necessary for the reduction of 50% of the anti-radical activity of gallic acid deduced from the curve is 0.37 µg/mL (2 µM). The antioxidant activity of gallic acid which is a strongly antioxidant synthetic molecule, validates the method chosen in the present work.

Anti-free radical activity of Staudtia kamerunensis var. gabonensis extracts

Evaluation of the anti-radical activity of the aqueous extract

According to the results obtained (Figure 2A), the anti-radical activity of the aqueous extract increased by 7.34 92 ± 0.254% for a concentration of 2.5 µgmL^-1 to approximately 90% for concentrations of 100 to 200 µgmL^-1. The IC₅₀ is 25 µgmL^-1.

Evaluation of the anti-radical activity of the cyclohexane extract

The percentage of antiradical activity increased slightly with the concentration of cyclohexane extract of S. kamerunensis var. gabonensis (Figure 2E). Indeed, it is 3.1 ± 0.309% for a concentration of 2.5 µgmL^-1; 8.63 ± 0.08% for a concentration of 25 µgmL^-1; 10.98 ± 1.54% for a concentration of 50 µgmL^-1 and only 26.25 ± 1.54% (IC₅₀/2) for a concentration of 200 µgmL^-1. The IC₅₀ of the cyclohexane extract would be around 400 µgmL^-1.

The anti-radical activity of the various extracts of the seeds of S. kamerunensis var. gabonensis was evaluated by trapping the ABTS•+ radical ion according to the method of Re et al. (1999) optimized by N'Negue et al. (2020) with gallic acid as reference antioxidant. The results of the antioxidant  activity  of  gallic  acid  (strongly antioxidant synthetic molecule) validate the chosen method. Moreover, the IC₅₀ value of gallic acid deduced from our results is more or less equivalent to that obtained by Sadat et al. (2011), which is 0.47 µg/mL and N’Negue et al. (2020, 2021) which is 0.47 and 0.37 µg/mL. These authors worked under the same conditions. The results of the evaluation of the anti-radical activity of the extracts of the seeds of S. kamerunensis var. gabonensis showed a variation of scavenging activity with the mode of extraction. Indeed, according to our results, the ethanolic extract which presents a strong antiradical activity, is the most active with an IC₅₀ of 20 µgmL^-1. The activity of the ethanolic extract is slightly higher than that of the aqueous and acetonic extracts, which presented quite similar activities with an IC₅₀ of 25 µgmL^-1.

However, according to the results obtained, the extracts of the apolar solvents "cyclohexane and trichlorethylene" have lower activities than those of the polar solvents "water, ethanol and acetone". The IC₅₀ of apolar solvents was greater than 200 µgmL^-1. We can explain these results by the presence of a large quantity of polyphenols in the polar extracts and their absence in the apolar extracts. Indeed, according to the literature, polyphenolic compounds are able to trap free radicals, which explain their strong anti-radical power (Biradar 2016; Nga et al., 2017; Becker et al., 2019).

The results of the phytochemical study of the seed extracts of S. kamerunensis var. gabonensis also showed the presence of tannins in the ethanolic and aqueous extracts and that of carotenoids in the acetone and ethanolic  extracts.  However,  the  carotenoids  were  not found in the aqueous extract but in the acetone and ethanol extract. These phytochemical results explain the slightly higher activity of the  ethanolic  extract  compared to the aqueous and acetone extract. Indeed, in the ethanolic extract, there is an abundant presence of polyphenols, tannins and an average presence of coumarins, flavonoids and then carotenoids which are recognized in the literature as high-level antioxidants because of their ability to trap free radicals such as singlet oxygen, superoxide free radicals and hydroxyl radicals (Treml and Smejkal, 2016; Kawamura et al., 2011; Jaswir et al., 2011; Anderson et al., 1996).

The very low quantity of carotenoids, coumarins, the total absence of polyphenols and tannins in the oils or fats of apolar extracts (extracts with cyclohexane and trichloroethylene) would explain their less significant antiradical activity.

This result corroborates that of Agnaniet (2004) who evaluated the antioxidant and antiradical activities of the essential oils of S. kamerunensis var. gabonensis by comparison with a commercial sample of di-t-buylhydroxytoluene widely used as a preservative. Biological screening for antioxidant action did not reveal significant activity, but a slight positive concentration effect was observed. The antioxidant activity of the seeds of S. kamerunensis var. gabonensis for IC₅₀ was 37% for a concentration of 666 µgmL^-1. The DPPH test showed a weak activity confirmed by the measurement of the antiradical activity which proved to be very weak compared to BHT. Agnaniet (2004) results indicate that the essential oils of S. kamerunensis var. gabonensis were much less active than the commercial sample. These essential oils are therefore of no interest in the fields of biotechnology.

However, according to our results, polar extracts are more active than apolar extracts. It seems that the more the extraction solvent is polar, the more it solubilizes the antiradical compounds. The activity of polar extracts is comparable to that of “reference antioxidant” gallic acid. Indeed, in the active ingredient responsible for the antiradical activity representing only about 10% of the total compounds of the extract, IC₅₀ of 20 or 25 µgmL^-1 of the total extract would be equivalent to an IC₅₀ of 2 or 2.5 µgmL^-1 of the active ingredient, which is only 5.4 or 6.75 times greater than that of the reference antioxidant, a pure chemical compound “gallic acid with IC₅₀ = 0.37 µgmL^-1”. Polar extracts would therefore have potential antioxidants.

The results showed that the total extract levels of oilseeds of S. kamerunensis var. gabonensis were 44.6%. The phytochemical tests carried out showed that the seeds of S. kamerunensis var. gabonensis are rich in major chemical groups such as alkaloids, tannins, polyphenols, flavonoids, reducing compounds, free anthracene derivatives, anthraquinones, total sugars, coumarins, free quinones, sterols, triterpenes, carotenoids and mucilages.

Strong anti-radical activity is observed with the ethanolic extract followed by the aqueous extract and with acetone. On the other hand, the cyclohexane and trichloroethylene extracts rich in fat or oil did not show significant antiradical activity. Extracts with high antiradical activity of S. kamerunensis var. gabonensis, because of their antioxidant properties, would therefore have preventive potential in the fight against pathologies associated with oxidative stress (cardiovascular diseases, aging, diabetes, cancer, inflammation, neuronal or genetic diseases). Moreover, these extracts could be used as natural antioxidants fighting against oxidation in the food, pharmaceutical and cosmetic industries.

The authors have not declared any conflict of interests.

The authors would like to thank the following institutions and laboratories: CENAREST/ IPHAMETRA, ENS, LaPluS in Libreville, Gabon.