Metabolites Profiling of Manilkara mabokeensis Aubrév Bark and Investigation of Biological Activities

Manilkara mabokeensis Aubrév is a tree that belongs to the Sapotaceae family, native to the tropical forest in Latin America, Asia, Australia, and Africa. The bark of this species is used as traditional medicine to treat diseases. The present study is the first phytochemical investigation on M. mabokeensis Aubrév bark in terms of phytochemical composition and bioactivity. Among the different extracts, ethyl acetate (EtOAc) exhibited the highest values of total phenolic content (TPC), total flavonoid content (TFC), condensed tannin content (CTC), and reducing sugar content, as well as a high antioxidant activity. Interestingly, gas chromatography-flame ionization detector (GC-FID) and gas chromatography-mass spectrometry (GC-MS) analysis were enabled to identify 23 compounds in the essential oil of M. mabokeensis Aubrév bark, which have not been previously described in the literature. Phytol and 8,14-cedranoxide were the major identified compounds, with area percentages of 27.9 and 18.8%, respectively. For HPLC analysis, 3,4-dihydroxy-benzoic acid methyl ester showed the highest concentration with 61.8 mg/g of dry residue (dr) among other identified molecules. Manilkara mabokeensis Aubrév bark MeOH extract showed a good anti-15-lipoxygenase (anti-15-LOX) and anti-acetylcholinesterase (anti-AChE) activities of 65.8 and 71.0%, respectively, while it exhibited a moderate antixanthine oxidase (anti-XOD) activity (41.5%) at 50 μg/mL. Furthermore, cyclohexane (CYHA) and ethyl acetate induced the highest cytotoxicity against the human ovarian cancer cell lines, OVCAR (49.5%) and IGROV (48.7%), respectively. Taken together, obtained results argue that M. mabokeensis Aubrév bark is an excellent source of natural compounds and justify its use in folk medicine.


Introduction
e Central African region is particularly highly endowed with diverse vegetation types. is region is the home of about 40.850 plant species, in which 6.000 are considered as endemic species, constituting tropical rainforests and coastal and alpine forests [1]. Nowadays, medicinal plants are attracting increasing attention. ese plants have been known to have effective utilities and most of the rural population depends on them in primary healthcare [2].
Ethnomedicinal studies play a vital role to discover new drugs from indigenous medicinal plants. Sustainable pharmacy is getting more popular and vast opportunities for new drug discoveries are provided by the unmatched availability of chemical diversity and natural products, either as pure compounds or as homogenous plant extracts [3]. erefore, plants have been used as source of remedies for the treatment of many diseases since ancient times and people of all continents, especially Africa, have this old tradition [4]. Medicinal plants are in great demand by the population thanks to their safety, effectiveness, lower costs, and biological activities. e genus Manilkara includes 135 plants that are distributed worldwide, of which about 20 can be found in tropical Africa [5]. ese species can be the roots of different chemical compounds belonging to different classes, including phenolic acids, flavonoids, and terpenes [6]. is genus includes many species with economic and therapeutic importance. Bark is used to treat diarrhoea and dysentery, while the leaves are endowed by antimicrobial and antioxidant activities [7]. Moreover, the Manilkara plant genus is recognized for its latex and chewing gum production [8]. Manilkara mabokeensis Aubrév, commonly known as Maboké sapodilla or Monghinza (Central African Republic), is a 25 m tall tree with a trunk diameter that can reach 100 cm [9]. is tree grows wild in the central African countries, especially Gabon and Central Africa [10]. In the past, M. mabokeensis Aubrév wood has been used in the construction of hunting elements (bow, crossbow, and trigger) [11]. To the best of our knowledge, there are no reports about the antioxidant and biological characterization of M. mabokeensis Aubrév bark, except our last work about the antimicrobial activity of M. mabokeensis Aubrév [12]. For that reason, this work was conducted to evaluate the chemical composition of organic extracts and essential oil, as well as the different biological activities (DPPH, 15-LOX, AChE, XOD, and cytotoxicity) of M. mabokeensis Aubrév bark.

Plant Collection.
e bark of M. mabokeensis Aubrév (Sapotaceae) was collected from trees growing spontaneously in their natural habitats in October 2012. e trees originate from the region of Boukoko situated in the southwest of Central African Republic (CAR). e tree was identified using an authenticated herbarium and samples of its bark were dried in the laboratory at ambient temperature. A voucher specimen was deposited at the laboratory of Analysis, Architecture and Reactivity of Natural Substances (CAR), under the number of Mm012. e dried bark was ground using a mixer into fine powder.

Preparation of the Plant Extracts and Essential Oil.
200 g of fine powder was successively extracted using 4 solvents of increasing polarity (CYHA, DCM, EtOAc, and then MeOH). A magnetic stirrer was used for extraction, which lasts 4 hours for each solvent. After filtration, each filtrate was evaporated using a rotary evaporator under vacuum at 35°C. e different residues obtained were evaluated for their chemical composition and their biological activity. For the essential oil, a hydrodistillation procedure was used. A mass of bark powder (50 g) was used for extraction by hydrodistillation using a Clevenger-type apparatus during 4 h in the Laboratory of Analysis, Architecture and Reactivity of Natural Substances (CAR).

Quantification of Total Phenolic Content (TPC).
e TPC of M. mabokeensis Aubrév bark extracts was determined using a Folin-Ciocalteu method, with minor modifications [13]. Briefly, the reaction mixture containing 20 μL of diluted plant extract (0.5 mg/mL) and 100 μL of Folin-Ciocalteu reagent (0.2 N) was left at room temperature for 5 min before adding 80 μL of sodium carbonate (75 g/L in water). After 25 min of incubation at ambient temperature, the absorbance was measured at 765 nm, using a microplate reader (Multiskan Go, F1-01620, Finland). A standard calibration curve was obtained using gallic acid (0-115 μg/mL). Results were expressed in milligram of gallic acid equivalents per g of dry residue (mg GAE/g dr).

Quantification of Total Flavonoids Content (TFC).
e TFC, in the various extracts, was estimated according to the Dowd method as described by Kohoude et al. [14]. A volume (100 μL) of the diluted extract (0.5 mg/mL) was mixed with 100 μL 2% solution of aluminum trichloride (AlCl 3 ) in MeOH. After an incubation of 15 min, the absorbance was measured at 415 nm against blank sample (MeOH). Quercetin (2-10 mg/L) was used as reference compound to allow drawing the standard curve. e results were expressed in milligram of quercetin equivalents per g of dry residue (mg QE/g dr).

Quantification of Total Condensed Tannin Content (CTC).
e determination of the CTC in the different extracts was done using the same procedure described by Kohoude et al. [14]. e diluted solution of each extract (50 μL) was mixed with vanillin (1% in 7 M H 2 SO 4 , 100 μL) in an ice bath. After that, the mixture was shaken and incubated at ambient temperature for 15 min. e absorbance of the samples was measured at 500 nm. Catechin (3-16 mg/L) was used as reference to make the calibration curve. e results were expressed in milligram of catechin equivalents per g of dry residue (mg CE/g dr).

Quantification of Total Anthocyanins Content (TAC).
e TAC contained in the various extracts of M. mabokeensis Aubrév bark was determined using the pH differential absorbance method as described by Kohoude et al. [14]. Two buffer solutions were prepared: e first solution consisted of hydrochloric acid (pH � 1.0) and potassium chloride (0.2 M). e second buffer solution was a mixture of acetic acid (pH 4.5) and sodium acetate (1 M). Briefly, 180 μL of the buffer solution was added to 20 μL of 2 International Journal of Analytical Chemistry extract. e reading was made on two wavelengths at 510 and 700 nm after 15 min of incubation. e following equation was applied for the calculation: A � [(A 510 -A 700 ) pH 1.0 -(A 510 -A 700 ) pH 4.5 ]. e results were expressed in milligram of cyanidin-3-glucoside equivalents per g of dry residue (mg C3GE/g dr).

Quantification of Reducing Sugar Content.
e sugar content quantification of M. mabokeensis Aubrév bark extract was done according to the procedure used by Kouhoude et al. [14], with minor modifications. Briefly, 100 μL of each extract at 5 mg/mL was mixed with 150 μL of DNS solution (0.05 M).
en, 750 μL of deionised water was added after stirring and incubation for 5 min in a bathhusband at 100°C. After a second stirring, the absorbance of the mixture was measured at 530 nm against a blank consisting of the same sample, in which the DNS was replaced by 5% DMSO, and against a negative control wherein the extract was replaced by 5% DMSO. e amount of sugar was determined in mg of glucose equivalent per gram of dry residue (mg GAE/g dr).

Essential Oil Analysis.
e chemical identification and quantification of M. mabokeensis Aubrév bark essential oil were done following the procedures of Kohoude et al. [14]. Gas chromatography-flame ionization detection (GC-FID) analyses were carried out on a Varian Star 3400-x chromatograph (France) fitted with a fused silica capillary DB-5MS column (5% phenylmethylpolysiloxane, 30 × 0.25 mm, film thickness 0.25 μm). Chromatographic conditions were, firstly, from 60 to 260°C, and then the temperature rose with a gradient of 5°C/min and 15 min isotherm at 260°C. After that, a second gradient was applied to 340°C at 40°C/min. For analysis reasons, petroleum ether was used to dissolve the essential oil. One microliter was injected in the split mode ratio of 1 : 10 and the helium was used as carrier gas at 1 mL/ min. e injector was operated at 200°C. For the gas chromatography-mass spectrometry (GC-MS) system (Varian Saturn 2000 ion trap GC/MS with CP-3800 GC), it was used with the same chromatographic conditions as GC-FID. e MS system was adjusted for an emission current of 10 μA and electron multiplier voltage between 1400 and 1500 V. e trap temperature was 250°C and that of the transfer line was 270°C and the mass scanning was from 40 to 650 amu. e identification of the compounds was done by (i) comparison of their retention index (RI) relative to C5-C24 n-alkanes obtained on a nonpolar DB-5MS column, with those provided in the literature, and (ii) comparison of their mass spectra with those recorded in NIST 08, reported in published articles or by coinjection of available reference compounds. e percentage composition of the essential oil was measured by the normalization method from the GC peak areas, assuming identical mass response factor for all compounds.

Organic Extracts Analysis.
e volatile compounds identification from the different organic extracts, before or after derivatization, was carried out with the same equipment GC-MS. e analysis was done following this gradient: 5 min at 60°C, then 60-270°C at 15°C/min, 6 min at 270°C, 270-300°C at 50°C/min, and finally 300°C at 4.5 min. e entire chromatographic program lasted 30 min. e derivatization method was that described by Kohoude et al. [14], with minor modifications.

Determination of DPPH Radical Scavenging Activity.
e free radical 2,2-diphenyl-1-picrylhydrazyl (DPPH) was used for antioxidant activity by applying the method used by Rahmani et al. [13], with some modifications. 20 μL of various dilutions of the plant extract was mixed with 180 μL of a 0.2 mM DPPH solution (dissolved in MeOH). e incubation lasted 30 min at 25°C, and the absorbance was measured at 520 nm. A blank was measured without extract. DPPH inhibition was calculated as % inhibition � 100 x (A blank -A sample )/A blank . . Human 15-LOX (from soybean) is the crucial enzyme that catalyzes the formation of bioactive leukotrienes (LT4A) from arachidonic acid (biological substrate) [15]. In this experiment (in vitro), linoleic acid (substrate) was oxidized to conjugate diene by 15-LOX. Briefly, 20 μL of diluted extract (0.5 mg/ mL) was mixed with 170 μL of Na 3 PO 4 buffer (pH � 7.4), 60 μL of linoleic acid, and 20 μL of enzyme solution . e absorbance was measured at 234 nm. A blank was measured without extract. Nordihydroguaiaretic acid (NDGA) was used as positive control. e enzyme activity inhibition was calculated as follows: % inhibition � 100 x (A blank -A sample )/A blank .

Antiacetylcholinesterase Activity (AChE).
e AChE activity was determined using the Ellman colorimetric method as previously described by Kohoude et al. [14]. Quickly, 50 μL of 0.1 mM sodium phosphate buffer (pH � 7.5), 125 μL of DTNB, 25 μL of diluted plant extract (0.5 mg/mL), and 25 μL of enzyme solution were mixed and incubated for 15 min at 25°C. Subsequently, 25 μL of ACTHi was added, and then the final mixture was incubated for 25 min at 25°C and the absorbance was measured at 421 nm. A blank was measured without extract. e reference used was galanthamine.
e enzyme activity inhibition percentage was calculated as follows: (1)

Xanthine Oxidase Inhibition Assay (XOD).
e XOD activity using xanthine as the substrate was evaluated using the procedure of Kohoude et al. [14]. e substrate solution (1 mM) was prepared by dissolving xanthine in 25 mL of 0.1 mM sodium phosphate buffer (pH � 7.5). e xanthine oxidase enzymatic solution was prepared by diluting xanthine oxidase enzyme from cow's milk (1 U) to a final concentration of 0.1 U/mL. e assay mixture consisted of 50 μL of diluted plant extract (0.2 mg/mL), 60 μL of 70 mM sodium phosphate buffer (pH � 7.5), and 30 μL of the enzymatic solution, giving a final extract concentration of 50 μg/mL in each well of a 96-well microplate. After an incubation of 25 min, 60 μL of substrate solution was added and the absorbance was measured at 295 nm after 5 min. A blank was measured without extract. Allopurinol was used as a positive control. e XOD activity was expressed as percent inhibition of XOD enzyme, calculated as follows: % inhibition � 100 x (A blank -A sample )/A blank .

Cytotoxicity Evaluation.
e cytotoxicity of the different M. mabokeensis Aubrév bark extracts was estimated on IGROV and OVCAR cells lines (American Type Culture Collection) as described by Kohoude et al. [14], with minor modifications. Cells were distributed in 96-well plates at 3 × 10 4 cells/well in 100 μL. After that, 100 μL of the corresponding culture medium (DMEM) containing sample at various concentrations was added. Cell growth was estimated by the MTT assay. MTT is a water-soluble tetrazolium salt with a yellow coloration. Metabolically active cells are able to convert the dye to water-insoluble dark blue formazan by reductive cleavage of the tetrazolium ring. e extracts were resolubilized in the DMSO followed by dilution in the buffer, whereby the DMSO does not exceed 1%. Doxorubicin was used as a positive control. e cells activity inhibition percentage was calculated as follows:

Extraction Yields and Chemical Composition of Extracts.
e extraction yield, the sugar content, the total phenolic content (TPC), total flavonoid content (TFC), condensed tannin content (CTC), and total anthocyanin content (TAC) in the M. mabokeensis Aubrév bark extracts are shown in Table 1. According to the literature, no studies have been reported previously on the effect of solvents on extraction yield of M. mabokeensis. In this study, four different solvents, namely, CYHA, DCM, EtOAc, and MeOH, were used for the extraction. e yields of the extracts obtained varied from 0.8 to 25.0%, according to the solvent used. For all the tested extracts, MeOH extract gave the highest yield (25%), followed by CYHA extract (1.7%), then EtOAc (1.2%) extract, and finally DCM extract (0.8%) ( Table 1). In general, the yield of the polar extract (MeOH) was twenty times higher than the yield obtained with DCM and was about fifteenfold greater than those of CYHA and EtOAc solvents. is difference of yields between the extracts could be due to the difference in chemical composition of extract, which allows us to suggest that the various extracts may contain more polar compounds. e present results were within the range of those found by Monisha et al. [16], when working on the bark extracts of M. hexandra. ey confirm that the highest yield was found in the polar solvents (water and MeOH). e contents of reducing sugars (mg/g dr) in various extracts of M. mabokeensis varied according to the polarity of solvents used. While the CYHA and DCM extracts showed no reducing sugar content, EtOAc and MeOH ones revealed contents of 78.7 and 101.1 mg GAE/g dr, respectively (Table 1).
According to the literature, the mentioned amounts of chemical family of M. mabokeensis Aubrév bark are evaluated for the first time. Statistically, bark extracts of M. mabokeensis showed no significant difference between CYHA and DCM solvents compared to the EtOAc and MeOH ones in terms of their TPC. e EtOAc extract had the TPC in the samples (354.2 mg GAE/g dr), whereas CYHA and DCM extracts contained a small amount of TPC, with 0.9 and 10.2 mg GAE/g dr, respectively. e present results were in accordance with those found in the different extracts of M. rufula stem bark. Similarly, the EtOAc extract had the highest TPC compared to the other extracts with different polarities [17]. e current results showed a high TPC compared to M. zapota ethanolic extract as found by Hilma et al. [18]. ey found a TPC that did not exceed 15 mg GAE/g dr.
While two extracts (EtOAc and MeOH) were found to exhibit flavonoids content, three extracts (DCM, EtOAc, and MeOH) highlighted tannin content. Statistically, there was a significant difference between the different extracts in terms of both TFC and CTC (Table 1). e condensed tannin content ranged between 2.0 and 9.9 mg CE/g dr, while the TFC did not exceed the 8.0 mg CE/g dr. In addition, the results showed that M. mabokeensis bark contained traces of anthocyanins. Among all tested extracts, only CYHA extract exhibited a low TAC of 0.03 C3GE/g dr (Table 1).

Identification of Volatile Compounds of the Essential
Oil. In Table 2, the percentages of the compounds identified in the essential oil from the bark of M. mabokeensis are listed in sequence of their retention indices (RI). In total, 23 compounds were detected and identified, representing 99.92% of the total oil with 2.55% monoterpene hydrocarbons, 2.03% oxygenated monoterpenes, 21.27% sesquiterpene hydrocarbons, 42.94% oxygenated sesquiterpenes, and 31.13% others.
is is the first report to investigate the chemical composition of the M. mabokeensis Aubrév bark essential oil and all the identified molecules were detected for the first time in Manilkara genus. e main constituents were found to be phytol and 8,14-cedranoxide, which were the major compounds, with area percentages of 27.19 and 18.88%, respectively. Other main components included two sesquiterpene oxygenated (caryophylleneoxide and 10-epic-eudesmol) and three sesquiterpene hydrocarbon (α-gurjunene, cyclosativene, and cis-thujopsene) with area percentages of 5.86, 5.84, 7.39, 6.54, and 4.79%, respectively ( Table 2). e number of monoterpenes was minor, compared to the sesquiterpene, with only six identified compounds. Eucalyptol and α-fenchene exhibited the highest area percentages of 1.56 and 0.81%, respectively.

Identification of Volatile Compounds of the Different Extracts by GC-MS.
e volatile compounds of M. mabokeensis Aubrév bark extracts were identified by GC-MS. No volatile compounds were detected in the EtOAc and MeOH extracts without derivation. However, four volatile compounds were detected in the CYHA and DCM ones. ese compounds were distributed as follows: trans-sesquisabinene hydrate and cedrene in the CYHA extract and 8-cedren-13-ol detected in the DCM one. Meanwhile, α-copaene compound was detected in both extracts (Table 3). Trying to identify more volatile compounds in the different extracts, a derivatization reaction was used. Overall, 10 volatile compounds were identified in the different organic extracts (Table 3). Only one derivatized compound International Journal of Analytical Chemistry (phenol,2-(1,1-dimethylethyl)-6-methyl-) was observed in the DCM extract. On the other hand, this step led to the identification of 3 volatile compounds in both CYHA and EtOAc extracts and 5 compounds in the MeOH one. All the compounds were detected only in one extract. However, catechin was detected in both EtOAc and MeOH. According to the literature, the GC-MS analysis before and after derivatization is the first such study of the extracts of a plant of the Manilkara genus and none of the identified molecules have been previously mentioned in the literature for this plant.  Figure 1). e concentrations of the identified compounds ranged from 0.06 to 61.76 mg/g dr. e compound 3,4-dihydroxy-benzoic acid methyl ester [20] was found in EtOAc and MeOH extracts with concentrations of 61.8 and 1.9 mg/g dr, respectively. While 4-hydroxy-3-propylbenzoic acid methyl ester [21] compound was detected in three different extracts (CYHA, DCM, and MeOH) with the same concentration (0.3 mg/g dr), the other two compounds (3-amino-4hydroxybenzoic acid [19] and 3,6,3′-trimethoxyflavone [22]) were found only in one extract (Table 4). According to the literature, none of the identified compounds were found previously in Manilkara species.

Biological Activities.
is is the first study to investigate the antioxidant, anti-15-LOX, anti-AChE, anti-XOD, and cytotoxic activities of M. mabokeensis extracts.    Figure 2). However, the DCM extract showed poor activity with IC 50 � 482.5 μg/mL and the CYHA extract was not active. Pearson's correlation coefficient, presented in Table 5, was determined by correlating the antioxidant activity inhibition and total amount of secondary metabolite classes. ere was a low negative correlation between TPC-anti-DPPH, TFC-anti-DPPH, CTC-anti-DPPH, and TAC-anti-DPPH, with r-values of −0.51, −0.55, −0.38, and −0.36, respectively (Table 5). ese findings indicate, probably, that the antioxidant effect of the different extracts could be due to other compounds besides the phenolic one. e present results were better than those found by Dutta and Ray [23]. In this study, the MeOH extract of M. hexandra bark showed an IC 50 of 88.7 μg/mL. Furthermore, a recent study, conducted by Chunhakant and Chaicharoenpong [24] showed that the IC 50 of the MeOH and the aqueous bark extract of M. zapota were 66.4 and 78.0 μg/mL, respectively. erefore, its antioxidant potency was less important than that of the bark MeOH extract of M. mabokeensis Aubrév (IC 50 : 18.7 μg/mL). Moreover, a previous study showed that some compounds, such as taraxerol and taraxerone extracted from M. zapota bark, have a high antioxidant activity and an IC 50 close to that in the current study [25].

Anti-15-LOX Activity. Manilkara mabokeensis
Aubrév bark extracts showed an anti-15-LOX inhibition effect ranked from 0 to 65.8% for the bark. Statistically, there was a significant difference (p ≤ 0.05) between the different extracts, regardless of the used solvent, in terms of 15-LOX inhibition. e polar extract (MeOH) showed the highest inhibition percentage of 65.8%, while the nonpolar (DCM and EtOAc) ones showed a moderate inhibition that did not exceed 25.7% (Table 6). No previous studies have investigated the anti-inflammatory activity of the Manilkara species extracts and the inhibition of the 15-LOX. In addition, Pearson's correlation coefficient presented in Table 5 showed a positive correlation between the group of phenolic compounds (TPC, CTC, and TFC) and the 15-LOX inhibition with r-values of 0.59, 0.95, and 0.74, respectively (Table 5). It is possible that the observed correlation was due to the considerably high amounts of phenolic compounds in polar extracts. Furthermore, this suggests that the phenolic metabolites are probably responsible for the bioactivity of extracts [26].

Anti-AChE Activity.
e AChE enzyme is involved in the hydrolysis of the neurotransmitter acetylcholine, which contributes to the pathogenesis of Alzheimer's disease [27]. All the extracts, except the CYHA one, showed an anti-AChE activity. Statistically, there was no significant difference (p > 0.05) between DCM and EtOAc extracts compared to the MeOH one, in terms of anti-AChE inhibition. e MeOH extract showed the potent activity against AChE enzyme with an inhibition of 71.0%. e other extracts (DCM and EtOAc) showed moderate inhibition activities of 43.5 and 46.5%, respectively (Table 6). Previous studies suggested that there is a correlation between TPC and AChE inhibition activity [28], which is the case in this study. According to the correlation matrix, a good correlation was found between TPC-anti-AChE, TFC-anti-AChE, and CTCanti-AChE with r-values of 0.61, 0.69, and 0.72 (Table 5).

Anti-XOD Activity.
e xanthine oxidase enzyme is a flavoprotein that catalyzes the oxidation of hypoxanthine to uric acid. erefore, anti-XOD activity was evaluated as the formation of uric acid from xanthine. Among all tested extracts, EtOAc and MeOH extracts showed an anti-XOD activity, with inhibition percentages of 11.1 and 41.5, respectively (Table 5). e other extracts showed no anti-XOD activity (Table 6). Statistically, as shown in the correlation matrix, there was a significant modest correlation between TPC and anti-XOD activity (r � 0.56) and between CTC and anti-XOD activity (r � 0.59), while this correlation was high between TFC and anti-XOD activity (r � 0.71) ( Table 5).
ese results indicate that the flavonoids were the most potent compounds, which induce an anti-XOD activity [29].

Cytotoxic Activity.
e cytotoxic activity of M. mabokeensis extracts was assessed against two cell lines (OVCAR and IGROV) at 50 μg/mL. While the EtOAc extract showed the most potent cytotoxic activity against IGROV with an inhibition percentage of 48.7%, the CYHA extract was more active against OVCAR cell line (49.5%) ( Table 7). Statistically, the cytotoxicity of the different extracts depends on the solvent polarity. Pearson's correlation coefficient was determined by correlating the cytotoxicity against cancer cell lines and total amount of secondary metabolite classes. us, there was a high positive correlation between the TPC, TFC, CTC, and cytotoxic activity for IGROV cell line with r-values of 0.94, 0.91, and 0.86, respectively. However, only TAC was found to have a very high correlation with the cell line OVCAR (r � 0.99) (Table 5).
ese findings made it possible to suggest the  involvement of a set of phenolic compounds in the inhibition of the IGROV cells growth. Nevertheless, anthocyanins were the most responsible compounds in the inhibition of OVCAR cell line [30].    ( Table 8). OVCAR and TAC showed a negative correlation with both PC1 and PC2, which means that these two variables were correlated, probably, with the third axis (PC3). Overall, there was a strong positive correlation between OVCAR and TAC. TPC, TFC, and CTC positively contributed to an increase of potential inhibition against IGROV with Pearson correlation coefficients (r) equal to 0.94, 0.91, and 0.86, respectively. Finally, there was also a good correlation between XOD and 15-LOX having an r-value (Pearson correlation coefficients) of 0.98 (Table 5). e biplot figure (Figure 4) showed, firstly, that extracts were located, relative to TPC, TFC, TAC, and the different biological activities, on the basis of their chemical composition. Secondly, while EtOAc and MeOH were placed close to each other, CYHA and DCM were located separately ( Figure 4). Overall, EtOAc and MeOH extracts were located close to the majority of variables (TPC, TFC, CTC, 15-LOX, XOD, IGROV, and AChE). is indicates that the polyphenol compounds contribute to the inhibition of these mentioned activities. However, CYHA extract, which contained the highest content of TAC, was responsible for the cytotoxic activity against OVCAR cell line.

Conclusion
In this study, evaluation on the chemical composition and biological activity of the plant M. mabokeensis was carried out as well as a series of phenolic compounds in order to contribute to the valorization of medicinal plants in the Central African Republic. Polyphenols, tannins, flavonoids, anthocyanins, and sugars were measured in these plants.
ey are quantified for the first time from extracts of M. mabokeensis. Analysis of the essential oil of M. mabokeensis bark by GC-MS and GC-FID identified and quantified 23 volatile compounds. Qualitative analysis of the extracts by GC-MS led to 14 compounds identified in the extracts of this plant. Two molecules of those identified in the extracts contain aromatic nuclei and are known for their pharmacological properties: catechin and phenol,2-(1,1dimethylethyl)-6-methyl-. In vitro, antioxidant, inhibition of 15-LOX, AChE, XOD, and cytotoxic (against human cancer lines of IGROV and OVCAR) biological activities of the extracts of this plant were studied for the first time. us, the correlations between the biological activities and the chemical composition of the extracts of the plant studied were obtained. erefore, original results were obtained for the phytochemical study, the chemical composition of the essential oil, and the biological activities of M. mabokeensis.

Data Availability
e data used to support findings of this study are included within the article.

Conflicts of Interest
e authors confirm that they have no conflicts of interest with respect to the work described in this manuscript.