Physicochemical properties, nutritional value, and antioxidant potential of jackfruit (Artocarpus heterophyllus) pulp and seeds from Cameroon eastern forests

Abstract This work aimed to study the physicochemical, nutritional, and antioxidant characteristics of the pulp and seeds of the jackfruit collected in the East Cameroon region to reduce the malnutrition problems encountered in the said region. To achieve this work, we first administered a survey. We observed that 50 people from Bertoua knew the fruit among the 200 people surveyed. After that, the physicochemical characteristics and nutritional value of Artocarpus heterophyllus pulp and seeds from Bertoua were evaluated. Finally, the antioxidant compounds (total phenolic and flavonoid contents) and the antioxidant activities were evaluated through the DPPH free radical scavenging capacity, the ability to reduce ferric ions, and the hydroxyl radical scavenging ability using the aqueous, ethanolic, and hydro‐ethanolic extracts of these samples (pulp and seeds). Results (means ± standard deviation) were obtained in triplicate and analyzed statistically by the analysis of variance (ANOVA) at the 0.05 probability level. The results revealed that the jackfruit pulp has a water content (89.85% ± 0.49) significantly higher than that of seeds (60.075% ± 0.12). The pH of jackfruit pulp (5 ± 0) is significantly lower than that of seeds (6 ± 0). Jackfruit pulp had a carbohydrate content (54.39% ± 0.47) significantly higher than that of seeds (49.01% ± 0.43). The protein content of jackfruit pulp (18.35% ± 0.04) is lower than that of the seeds (21.66% ± 0.31). For mineral content, the maximum contents of K (848 mg/100 g ± 10.34) and Na (69.53 mg/100 g ± 0) were identified in the jackfruit pulp while those of Ca (132 mg/100 g ± 9.42), Mg (43.73 mg/100 g ± 9.12), and P (101.51 mg/100 g ± 4.02) were found in the seeds. However, all extracts possessed both antioxidant compounds (phenols and flavonoids) and antioxidant activities. In conclusion, the jackfruit appears to be a fruit that can improve the nutritional status of the populations of eastern Cameroon.


| INTRODUC TI ON
In Cameroon, as in most developing countries, the issue of malnutrition remains a challenge. Malnutrition is defined as deficiencies, excesses, or imbalances in a person's energy and/or nutritional intake. In Cameroon, 33% of children under the age of five suffer from chronic malnutrition (INS, 2020). In the East Cameroon region, 37% of children suffer from stunting and 65% of children aged 6-59 months have anemia (INS, 2020). The management of malnutrition is done through hospitalizations in nutritional centers. However, it is not effective because of the lack of competent personnel, the high cost of care, the inaccessibility of care in remote areas, or the shortage of therapeutic foods (Nguefack et al., 2015). One possibility to reduce this malnutrition is the valorization of local food products and more specifically forest fruits because their nutritional potential and their almost free availability make them accessible to all social classes (Kone, 2018).

The Eastern Region is one of the largest regions in Cameroon and
is an ecological area dominated by large trees and a diversity of plant species (Mengue, 2004); many fruits are little known and consumed by the population. They are generally underexploited but could constitute a significant source of nutrients. Among these fruits, we find the fruit of Artocarpus heterophyllus commonly called jackfruit, which is the largest known edible fruit. Studies conducted in India and Bangladesh have shown that jackfruit is a fruit rich in water and carbohydrates; however, its fat content is low. It contains micronutrients such as vitamins (thiamine, riboflavin, vitamin C, and vitamin A) and minerals (potassium, sodium, calcium, magnesium, and iron) necessary for the proper functioning of the human body (Goswami & Chacrabati, 2016;Haq, 2006). Jackfruit seeds are less widely known but have important nutritional value. Jackfruit seed contains moisture 21.10%-71.92%; fiber 0.94%-3.96%; ash 0.89%-3.16%; protein 10.09%-18.12%; and carbohydrate content 7.89%-30.84% (Kushwaha et al., 2023;Thatsanasuwan et al., 2023). Jackfruit seeds are used as a component of food formulations including gluten-free pasta made from jackfruit seeds (Thatsanasuwan et al., 2023), jackfruit seed flour-based waffle ice cream cone (Kushwaha et al., 2023), and jackfruit seed starch .
In Cameroon, there is no information related to this fruit; the nutritional values of a plant are a function of pedological and climatic factors, this study aimed to determine the physicochemical characteristics, the nutritional value, and the antioxidant properties of the pulp and seeds of the fruit A. heterophyllus to valorize it on a national scale and to contribute to improving the nutritional status of the populations of the East region in particular and of Cameroon in general.

| Knowledge and consumption surveys
A survey of knowledge and consumption of jackfruit was conducted in the city of Bertoua in the East Cameroon region. Approximately 200 people were randomly selected to be interviewed, but only 50 participated in the study. The criterion for inclusion in the study was knowledge of the fruit. It should be noted that the questionnaire developed was tested and then amended before printing the final version ( Figure 1). It was then administered using a participatory approach. The questionnaire was designed as shown by Bemmo et al. (2023) to provide information on: • Levels of knowledge of A. heterophyllus fruit; • Socio-cultural characteristics of respondents (age, gender, region of origin, educational level, and occupation); • Modes of consumption of the fruit of A. heterophyllus; • Common names of the fruit of A. heterophyllus; • Nutritional (fruit) and therapeutic qualities of A. heterophyllus; • Periods and techniques of harvesting the fruit of A. heterophyllus.

| Collection and preparation of samples
The plant material consisted of ripe fruits of A. heterophyllus ( Figure 2) harvested in the East Cameroon region, more precisely in the Mokolo III district (4°58′North and 13°40′East) of the city of Bertoua, the Bertoua II district and the Lom and Djerem department in July 2021. After harvesting, the fruits were sorted, cleaned (washed with soap and water), and then the pulp and seeds were extracted ( Figure 3). The seeds were then boiled for 20 min, and the pulp and boiled seeds were dried in an oven (MEMERT) at a temperature of 45°C. Finally, they were crushed.

| Physicochemical properties
The moisture content was determined according to the method of AOAC (1990). The ash content was evaluated by incineration of the sample for 20 h at 550°C according to the method of AOAC (1990). The determination of pH was made with a digital pH meter (HANNA HI 8424; Sadler & Murphy, 2010). The titratable acidity was determined in milliequivalent of NaOH per 100 g of dried matter (Sadler & Murphy, 2010). All analyses were carried out in triplicate.

| Nutritional value
For the determination of the protein content, Nitrogen (N) content was analyzed using the Kjeldahl method, and the protein content was calculated as N × 6.25. Lipid content (mg/100 g DM) was determined by using the Soxhlet method (Ijarotimi & Keshinro, 2013). The carbohydrate content was determined by different methods as reported by Ijarotimi and Keshinro (2013). The fiber content was determined by the AOAC method (1990). All analyses were carried out in triplicate.
The energy value of the fruits (in Kcal/100 g) was determined by the method of Ijarotimi and Keshinro (2013). First, the contents of dry matter, total protein, total fat (lipids), and ash were determined, then the carbohydrate content was calculated by difference, and finally the energy value was calculated by multiplying the contents of each component (in g) by the average caloric values (in Kcal) and sum. The energy value was determined by Equation 1: where, L is the lipid content; P is the protein content; C is thehydrolyzable carbohydrate content; and L, P, and C are expressed as a percentage of dry matter.

| Determination of mineral content: Ca, Mg, K, Na, and P
The minerals K, Ca, Mg, and Na were determined by atomic absorption spectrophotometry following the method of AOAC (2005).
Phosphorus was determined by the colorimetric method described by AOAC (2005).

| Antinutrient content
Phytate content, Oxalate content, and Saponin content were determined using the standard method of AOAC (2005).
(1) W(Kcal) = 9L + 4P + 4C F I G U R E 1 Consumption and knowledge survey form at the jackfruit.
The tannins contents (condensed tannins and hydrolyzable tannins) were evaluated as follows: Extraction of tannins: In a 50-mL Erlenmeyer, we introduced 2 g of samples and 30 mL of 80% acetone. After 15 min of agitation, the mixture was filtered, the residue washed twice, and the acetone has been separated from the filtrate using a Rotavapor at 35°C.
Determination of condensed tannin content: Condensed tannins were determined by following the method of Kassegn (2018).
Extracts were diluted to 20th before determination. The assay is performed in 15-mL test tubes previously covered with aluminum foil. One milliliter of diluted sample was introduced into each test tube followed by 3 mL of a freshly prepared solution of 4% vanillin in ethanol (w/v). The mixture was then shaken and 1 mL of concentrated HCl was added. The tubes were left at room temperature for 15 min and then the absorbance was read at 500 nm. The equation below was used to determine the absorbance of 100 g of dry matter in the delipidated samples.
where, F is the dilution factor; q is the number of tannins from each trial; DM is the dry matter content of samples analyzed; and m is the mass of the sample used for the extraction. where, TH is the hydrolyzable tannins; Abs is the Absorbance; M is the mass = 300; V is the volume of the extract used; E mole: 2169 (constant expressed in moles) P is the weight of the sample.

| Determination of total phenolic content
The total phenolic content of jackfruit samples was determined using the Folin-Ciocalteu colorimetric method, as described by Kassegn (2018). In a test tube of 5 mL volume, 0.01 mL of a 5 mg/ mL extract solution was added, followed by the Folin-Ciocalteu reagent (0.2 mL) and distilled water (1.39 mL). After 3-min incubation of the solution mixture at room temperature, 0.4 mL of 20% sodium carbonate solution was added and the mixture was re-incubated for 20 min under the same conditions. The absorbance of the resulting blue-colored solution was measured at 760 nm using a spectrophotometer (BioMate). The total phenolic content of the extract was calculated from the gallic acid standard curve and expressed as milligrams of gallic acid equivalent (GAE) per gram of extract. ( (3) TH = (Abs × M × V) ∕ Emole × P F I G U R E 2 Photograph of the fruits of Artocarpus heterophyllus harvested.

| Evaluation of antioxidant activities
The antioxidant activity was evaluated by three tests: the 2,2-diphenyl-1picrylhydrazyl radical (DPPH) free radical scavenging capacity, hydroxyl radical scavenging ability, and the ability to reduce ferric ion (FRAP test). Besides, the efficient concentration 50 (EC50) was determined according to the antioxidant activity.

Measurement of hydroxyl radical inhibition power (ROH)
The scavenging activity for hydroxyl radical produced by the Fenton reaction was measured using the orthophenanthroline method (Nagulendran et al., 2007). In this experiment, 60 μL of FeCl2 (1 mM 12.5 μg/mL) were mixed in the test tubes. The reaction was initiated with hydrogen peroxide and then incubated at room temperature for 5 min. After incubation, the absorbance of the mixture was recorded at 560 nm using the spectrophotometer (BioMate) against the blank prepared in the same conditions with distilled water. BHT solution was used as standard, and experiments were performed in triplicate.
An increase in the absorbance of the reaction mixture indicated an increase in the ability to reduce the hydroxyl radical.

Assessment of the ferric reducing antioxidant power (FRAP)
The

| Statistical analysis
Results (means ± standard deviation) were obtained in triplicate and analyzed statistically by the analysis of variance (ANOVA) at the 0.05 probability level. Fisher tests were used to compare means of physicochemical, nutritional, and antioxidant evaluations using the factor program of the XLSTAT 2007 statistical package.

| Physicochemical composition of fruits
The physicochemical composition of the pulp and seeds of the fruit of A. heterophyllus is presented in Table 1.

| Macronutrient composition
The macronutrient composition of the pulp and seeds of the fruit of A. heterophyllus is presented in Table 2.

| Energy value of the fruit
The energy value of jackfruit pulp and seeds is presented in Table 3.
From this table, we can be seen that the energy values of the different samples vary between 332.23 and 351.08 Kcal/100 g DM for boiled seeds and pulp, respectively.

| DDPH test
The evolution of the antiradical activity of the different extracts of the fruit of A. heterophyllus and vitamin C according to different concentrations is presented in Figure 4. It is observed that the antiradical activity varies according to the extracts and increases with the concentration. It is observed that by varying the concentrations from 25 to 100 μg/mL, the inhibition percentages of the different extracts of the pulp are similar and lower than that of vitamin C. But at 200 μg/mL, the aqueous extract shows the best activity. For boiled seeds, the inhibition percentage of the hydroethanolic extract is higher than those of the different extracts and lower than that of vitamin C whatever the concentration used (25-200 μg/mL). The aqueous extract shows the best antifree radical activity for the pulp while the hydroethanolic extract shows the best antifree radical activity for the boiled seeds.
The EC 50 of the different extracts is presented in for 20 μg/mL < EC 50 < 75 μg/mL, the antioxidant activity is moderate; and for EC 50 > 75 μg/mL, the activity is low;" the antioxidant activity of boiled seeds and pulp is low. However, the hydroethanolic extract of boiled seeds with the lowest EC 50 has the best activity.  compared to that of BHT is presented in Figure 6. It was found that by varying the concentrations from 25 to 100 μg/mL, the reducing powers of the different pulp extracts are all similar, but at 200 μg/ mL, the aqueous extract shows the best power. For boiled seeds, the reducing power of the ethanolic extract is higher than those of the different extracts whatever the concentration used (25-200 μg/ mL). However, it should be noted that the powers of the different extracts are all lower than that of BHT.

| DISCUSS ION
In the survey conducted, only 25% of the population interviewed knew jackfruit, which makes it a little-known fruit in the eastern region of Cameroon. Regarding the consumption of jackfruit, the study showed that 98% of the people who knew jackfruit consumed it, which means that people who knew jackfruit consumed it. Regarding the different forms of consumption of jackfruit, the study revealed that the pulp was consumed more than the seeds. The seeds were eaten in a burnt or boiled state, which oriented the study toward boiled seeds. In terms of the nutritional values of jackfruit, the study revealed that the participants did not know the nutritional benefits of jackfruit or their interest in this work.
The moisture content provides information on the shelf life of the food. The water content of the obtained pulp (89.85%) is higher than those of Goswami and Chacrabati (2016) who showed that in Bangladesh, the water contents of pulps of different jackfruit varieties were 80.95%-82.22%. It is also higher than that obtained by Ouatara (2015) on mango pulp in Burkina Faso (84.53%-85.91%).
However, the moisture content of boiled seeds (60.075%) is higher than that obtained by Abedin et al. (2012) in Bangladesh (51.6%-57.7%). These differences can be attributed to the cooking of seeds, climatic conditions, the nature of the soil, and the maturity of the fruit. This important water content of jackfruit pulp is a limitation for the storage time of this fruit, making it a perishable commodity. However, this high water content can also be beneficial in the production of juice in quantity. To preserve the jackfruit for a long period of time, techniques such as drying, keeping fresh, and processing into food products (jams, syrup, and chic) could be used.
The pH and titratable acidity provide information on the acidity level and organoleptic properties of food. The pulp pH value of 5 agrees with work conducted by Galvez and Dizon (2017)  Philippines that showed jackfruit pulp pH of 4.8-5.50. This result is lower than the 4.17 found by Ouatara (2015) in Burkina Faso on mango pulp. Similarly, the pH result of boiled jackfruit seeds (6) agrees with the work conducted by Ocloo et al. (2010) in Ghana who showed that jackfruit seeds had a pH of 5.78.
Proteins play a major role in our body because of their numerous functions. The highest protein content was observed in boiled seeds (21.66%), this result is largely superior to those obtained by Thatsanasuwan et al. (2023) who worked on jackfruit seeds in Thailand and obtained protein contents of 11.83%. However, regarding jackfruit pulp, the protein content obtained was 18.35%; this result is higher than those obtained by Rajneesh and Singh (2020) in India on jackfruit pulp (1.4%-2.3%). It is also higher than those found by Haq (2006) on jackfruit pulp in Bangladesh (1.2%-1.9%).
These differences can be attributed to several factors such as the genetic makeup of the plant, climatic conditions, fruit maturity stage, soil type, and sample preparation (Morris et al., 2004). The analyzed samples have a significant protein potential that could be exploited in human nutrition, especially in the production of baby food and livestock feed.
Carbohydrates are the most macronutrients in the human diet, with an intake between 45% and 50% (   Fibers are elements that participate in the proper functioning of intestinal transit. The highest fiber content was found in boiled jackfruit seeds (14.26%). This result is higher than that obtained by Ocloo et al. (2010) who worked on jackfruit seeds in Ghana and obtained a value of 3.19%. Regarding the pulp, the fiber content obtained was 9.88 which is higher than that of Haq (2006) who showed that jackfruit pulps in Bangladesh had fiber contents between 1% and 1.5%. This result is also higher than that (1.87%-2.77%) found by Traore (2020) on pineapple pulp in Burkina Faso. These high fiber contents make jackfruit harvested in Bertoua, Cameroon an essential food in the prevention of constipation, colon cancer, diabetes, and cardiovascular diseases (Bemmo et al., 2023).
Among the minerals analyzed, potassium was the mineral with the highest content in the pulp and boiled seeds of A. heterophyllus fruit (848.75 mg/100 g and 721.99 mg/100 g, respectively). Indeed, potassium is a very important mineral because it allows, among other things, to maintain the acid-basic balance, the osmotic pressure, and the conduction of nerve impulses. This high potassium content in jackfruit from Bertoua makes it an important source of potassium to prevent potassium deficiencies or for formulations. Potassium is also hypotensive and is also involved in muscle contraction (Dedehou et al., 2015) so consumption of jackfruit from Bertoua, Cameroon should be advised for people with high blood pressure.
Calcium is the second most encountered mineral in our samples. Calcium contents are 84 ± 5.65 mg/100 g for pulp and 132 ± 9.42 mg/100 g for seeds. Calcium is important for the construction and maintenance of bones, blood coagulation, transmission of nerve impulses, and formation of teeth and bones. It is also an important cofactor in enzymatic metabolic processes (Senga et al., 2013). The consumption of jackfruit pulp and seeds from Bertoua should be encouraged in growing toddlers and people suffering from osteoporosis (insufficient bone mineralization).
Phosphorus is the third most encountered mineral in our samples (43.22 mg/100 g for pulp and 101.51 mg/100 g for seeds). It helps strengthen bones and teeth. It is very essential for the fortification of children and nursing mothers (Andzouana & Mombouli, 2012).
Sodium is also a mineral found in the pulp (69.53 mg/100 g) and the seeds (57.6 mg/100 g) of the A. heterophyllus fruit harvested in Bertoua, Cameroon. It maintains the acid-base and osmotic balance between the cells and the interstitial liquid (Martin, 2001).
The analysis of the nutritional value of the different samples allowed us to say that jackfruit pulp and seeds from Bertoua, Cameroon are rich in macronutrients (carbohydrates, proteins, and fiber) and micronutrients (potassium, calcium, phosphorus, magnesium, and sodium).
However, when antinutrients are present in foods, they sometimes prevent the absorption of certain nutrients by several mechanisms. Thus, the content of some antinutrients has been evaluated in this study.
The antinutrients that were determined in our study were as follows: phytates, tannins, saponins, and oxalates.
Oxalates were the most common antinutrients found in our samples. A high concentration of oxalates in the diet could lead to kidney stones (Nwaogu & Emejulu, 2010). The analyses carried out showed that the boiled seeds and pulp of A. heterophyllus contained 40.5 and 39.08 mg oxalates/100 g, respectively. These results for jackfruit pulp from Bertoua are significantly lower than those obtained by Adetuyi et al. (2008) on papaya pulp (450 mg/100 g) in Nigeria.
Phytates prevent the absorption of iron, calcium, zinc, and magnesium. They must, therefore, be found in very small quantities in Tannins are substances that prevent the absorption of iron, a mineral that is very important for the proper functioning of the body.
The hydrolyzed and condensed tannin contents of boiled seed samples were, respectively, 9.87 mg/100 g and 3.54 mg/100 g. The hydrolyzed and condensed tannin contents of pulp samples were 4.13 mg/100 g and 2.49 mg/100 g. These results for jackfruit pulp from Bertoua are lower than those obtained by Adetuyi et al. (2008) on papaya: 21 mg/100 g hydrolyzed tannins and 62 mg/100 g condensed tannins in Nigeria.
Saponins are substances that are astringent at high concentrations and impart a bitter taste to fruits. High saponin levels have been associated with gastrointestinal enteritis manifested by diarrhea and dysentery (Datti et al., 2020). The saponin contents of the samples were 0.1 mg/100 g for boiled seeds and 0.02 mg/100 g for jackfruit pulp, respectively. These results obtained in the jackfruit pulp samples are lower than those of Umuru et al. (2007) who showed that the pulp of baobab fruit in Nigeria had a saponin content of 1.051 mg/100 g.
Given the above results, the jackfruit pulp and seeds from Bertoua contain lower antinutritional values than those of widely consumed fruits, so we can conclude that they are consumable.
The antioxidant activity of the different extracts by colorimetric determination of total phenols and flavonoids proved that the flavonoid contents of the fruits varied according to the aqueous, ethanolic, and hydroethanolic solvents. Total phenols and flavonoids are natural antioxidants. The highest content of total phenols was observed in boiled seeds (14.39 mg EAG/g extract). This result is lower than those obtained by Jagtap et al. (2010) who worked on jackfruit seeds in India and obtained a phenolic content of 27.7 mg EAG/g extract. However, the result of the phenolic content of pulp (13.82 mg EAG/g extract) is higher than those found by Soong and Barlow (2004); Jagtap et al. (2010) who showed that jackfruit pulps in Singapore and India had total phenolic contents of 0.9 and 0.46 mg EAG/g extract, respectively. This variation could be due to the complex nature of this group of compounds, the extraction, or the analysis method used (Kalt et al., 2001). It has been shown that the phenolic composition of the plant is influenced by intrinsic factors such as species and variety or by extrinsic factors such as environment and agronomy (Barberan & Espin, 2001). Regular consumption of jackfruit pulp and seeds from Bertoua could prevent oxidative stress-related disorders such as degenerative diseases.
Epidemiological and clinical studies have highlighted the potential role of flavonoids in reducing the risk factors for cardiovascular diseases, osteoporosis, and lung cancer (Lampila et al., 2009). In the analyses, the best solvent for the extraction of flavonoids in the pulp was water, this result agrees with the work conducted by Jagtap et al. (2010) on jackfruit pulp in India. On the other hand, the flavonoid content obtained in the pulp samples (7.01 mg EAG/g extract) is higher than that found by the same author in jackfruit pulp in India (1.2 mg RE/extract). The concentration of flavonoids in jackfruit is an asset for health since flavonoids, by their function, protect blood vessels from cholesterol damage and reduce oxidative stress (because they are antioxidants).
The antioxidant activity was also evaluated by three tests: the 1,1-diphenyl-2-picrylhydrazyl radical (DPPH) test, the FRAP test, and the ability to reduce the hydroxyl radical. Regarding the DPPH test, all the pulp extracts were able to reduce the DPPH radical; this result agrees with the studies conducted by Jagtap et al. (2010) who worked on jackfruit pulps in India. However, the EC 50 of the pulp sample from Bertoua (5.075-36.506 mg/mL) is higher than the one found by the same author in India on jackfruit pulp (0.4-0.7 mg/mL).
The antioxidant-reducing power of ferric ions is the simplest, quickest, and cheapest method for routine analysis. The analyses performed showed that all extracts (pulp and boiled seeds) have ferric ion-reducing power; however, these reducing powers are lower than that of BHT. These results are contrary to those obtained by Jagtap et al. (2010) who demonstrated that at low concentrations (1-3 mg/mL) all extracts of jackfruit pulp in India had higher ferric ion-reducing powers than vitamin C. These differences can be attributed to the method used.
Jackfruit pulp and seeds from Bertoua, Cameroon, have excellent natural antioxidants that could be used to fight oxidative stress.

| CON CLUS ION
This study revealed that jackfruit (Artocarpus heterophyllus) pulp and seeds from Bertoua, Eastern Region, Cameroon, have important nutritional value and antioxidant properties exploitable in human nutrition. Hence, they can be used to improve the nutritional status of the populations in this region where the malnutrition level is still high. According to its high energy value (more than 300 Kcal/100 g), jackfruit from Bertoua, Cameroon, could be

ACK N O WLE D G E M ENTS
The authors thank Professor Zambou François who kindly allowed this work to take place in his Research Unit.

CO N FLI C T O F I NTER E S T S TATEM ENT
The authors confirm that they have no conflicts of interest concerning the work described in this manuscript.

DATA AVA I L A B I L I T Y S TAT E M E N T
There are no primary data associated with this manuscript.

E TH I C S S TATEM ENT
All panelists enrolled in this study provided written informed consent. Also, they were informed that they can withdraw from the evaluation at any time without giving a reason.