This study was conducted in South Kivu Province, in eastern DRC. South Kivu is one of 26 provinces in the DRC. It is located in the eastern part of the country and covers an area of 65,070 km², or about one-third of the country. It is bordered to the north by the North Kivu Province, to the west by Maniema Province, to the south by Tanganyika and Maniema Provinces, and to the east by the neighboring republics of Rwanda, Burundi and Tanzania. The province is subdivided into eight territories: Fizi, North Idjwi, South Idjwi, Kabare, Kalehe, Mwenga, Shabunda, and Walungu. It is located approximately between 1˚36' and 5˚ south latitude on the one hand, and 26˚47' and 29˚20' east longitude on the other [6] [7] .

This study was conducted on four local varieties of wild edible plants used in the territory of Kabare and its surroundings in the province of South-Kivu. The four species are used for several purposes such as nutrition and traditional medicine for the treatment of various diseases, including women’s infections and skin diseases [5] . The Ensete ventricosum (Musaceae), is renowned for the quality of the product obtained from preparation in an aqueous medium in terms of colour and taste, while the other three, namely Aframomum laurentii (Zingiberaceae), Portulaca oleracea (Portulacaceae) and Myrianthus holstii, are domesticated for their high yield and disease resistance and medicinal use (based on our surveys).

Five plant samples (three leaf samples and two seed samples) from four species of wild edible plants were analysed in this study. They were collected in three villages: Kadjuchu, Lwiro and Tschivanga in the Kabare territory of South Kivu. Sampling was carried out at ten-day intervals over a month during the ripe season for each plant. After collection, samples of more than ten kilograms were transported to the malacology laboratory of the Lwiro Natural Sciences Research Centre (CRSN-Lwiro). At the laboratory, the seeds were extracted and dried in the open air to prevent them from rotting while awaiting sample processing ( Figure 1 ). The figure below gives different plant samples used during this study.

Samples of the four wild edible plants were collected, washed, cut into slices (approximately 5 mm) separately, then dried in an oven (Binder GMBH, Model: M-115, Germany) at 70˚C until a constant weight was achieved. The dried samples were then finely ground using a laboratory mill and stored in airtight plastic jars. They were then kept in desiccators for further analysis at the malacology laboratory of the Centre for Natural Science Research (CRSN) in Lwiro.

1) Moisture content

The moisture content was determined using the Association of Official Analytical Chemists [8] method, official method 930.15, in which empty crucibles were washed and then dried in an oven for 72 hours in desiccators, after which they were weighed (W₁). Approximately 40 g of the sample were weighed accurately (W₂) in a previously weighed crucible, each step being carried out in desiccators. The crucible containing the sample was then placed in an oven (Binder GMBH, Model: M-115, Germany) at 70˚C for 42 hours, until a constant mass was obtained. After cooling to room temperature in the desiccators, the crucibles were weighed again (W₃). The moisture content was determined using the following equation

$\text{Moisture content}=\frac{{\text{W}}_2-{\text{W}}_3}{{\text{W}}_2-{\text{W}}_1}\times 100$ (1)

2) Ash content

The ash content was determined using the [9] method, official method 923.03. We weighed 5 clean crucibles and dried them at 105˚C in an oven for 2 hours. They were then cooled in desiccators and weighed (W₁). After that, 3 g of sample was weighed into a pre-weighed crucible (W₂). The crucibles containing the samples were then incinerated in a muffle furnace (Stuart SF, United Kingdom) at 550˚C for 2 hours, until a light grey ash was obtained. After cooling, they were weighed (W₃). To calculate the ash content, we used the formula:

$\left(\%\right)=\frac{{\text{W}}_3-{\text{W}}_1}{{\text{W}}_2-{\text{W}}_1}\times 100$

3) Crude fat content

The crude fat content was determined using the Soxhlet extraction method [10] , official method 2003.06. After drying the aluminum cups containing boiling stones in an oven at 105˚C for 30 minutes, they were cooled in desiccators at room temperature and then weighed (W₁). We then weighed 5 grams of sample into extraction cartridges and extracted with 70 ml of diethyl ether. After extraction, we removed the cups from the extractor and dried them in an oven at 105˚C for 30 minutes to evaporate the solvent. We then cooled them in desiccators for 30 minutes and immediately weighed them (W₂). The amount of fat obtained was expressed as a percentage of the initial weight of the sample using the following formula:

$\text{Crud fat content}\left(\%\right)=\frac{{\text{W}}_2-{\text{W}}_1}{\text{SW}}\times 100$

where SW: sample weight.

4) Crude fiber content

The crude fiber content was determined according to the International Organisation for Standardisation (ISO 5498) (2002) method [8] [10] [11] . We weighed 2 grams of sample, transferred it to a 600 ml beaker, and boiled it with 200 ml of 1.25% sulphuric acid for 30 minutes. After digestion with 20 ml of 28% caustic soda (NaOH) for 30 minutes, we filtered the mixture using a vacuum pump through a crucible containing a layer of sea sand, then washed the residues five times with hot distilled water. The residue was then washed three times under vacuum, each time with 30 ml of 1% sulphuric acid solution, followed by distilled water, 1% soda solution, distilled water and finally acetone, then dried by suction. We then dried the residue in an oven at 130˚C for 2 hours, cooled it in desiccators and weighed it (W₁). After incinerating the samples in a muffle furnace at 550˚C for 2 hours, we cooled them again in desiccators and weighed them (W₂) [8] [10] . To calculate the fiber content, we used the following formula:

$\text{Crude fiber content}\left(\%\right)=\frac{{\text{W}}_1-{\text{W}}_2}{{\text{W}}_3}\times 100$

where

W₁ = Weight of crucible + residues before incineration.

W₂ = Weight of crucible + ashes after incineration.

W₃ = Weight of initial sample.

5) Crude protein content

The crude protein content was determined using the Kjeldahl method [9] , in which 1 g of sample was weighed into a digestion flask, then 12 ml of concentrated sulphuric acid (H₂SO₄) was carefully added. Next, we took 3 ml of 30% hydrogen peroxide (H₂O₂) and added it gradually after mixing thoroughly. Once the violent reaction had stopped, the flasks were shaken, then 3 g of catalyst (a mixture of copper sulphate and potassium sulphate) was added, and digestion was carried out by heating to 420˚C. Once the digestion was complete, we connected the flasks to another receiving flask containing 2% boric acid and indicators (methyl red and bromocresol green). The solution in the digestion flask was then made alkaline by adding 40% sodium hydroxide (NaOH), which released ammonia (NH₃) into the receiving flask, where it reacted with the boric acid to form a borate ion. Finally, we titrated the distillate with a standard 0.1 M HCl solution, and the crude protein content was calculated based on Total Nitrogen, in accordance with the AOAC method (2016).

(%) Total Nitrogen = [V_HCl – V_HCl × N_HCl × 1.401]/P

where: V_HCl = Volume of hydrochloric acid for the sample (ml), N_HCl = Normality of hydrochloric acid = 0.9516, Vo = Volume of hydrochloric acid added to the blank (ml), Conversion factor = 6.25, Constant = 1.401, Test sample = 1 gram.

6) Total carbohydrate content

To determine the percentage of total carbohydrates, we added up the crude protein, crude fat, moisture and ash contents of the sample, then subtracted them from 100%. The following formula was therefore established:

Total carbohydrates (%): 100 − (M + P + F + A) where: M: moisture content, P: protein content, F: fat content and A: ash content [8] [9] .

7) Mineral analysis

The analysis of secondary metabolites focused on the following species: Aframomun laurentii, Portulaca oleracea, Ensete ventricosum, and Myrianthus holstii.

Phytochemical screening was performed to identify ten secondary metabolites, including saponins, alkaloids, flavonoids, tannins, terpenoids, steroids, glucosides, phenols, quinones and lipoids. These bioactive compounds were analysed using the qualitative analytical methods described for the detection of each active ingredient sought, which was identified either by the appearance of a characteristic colour, or by the formation of a precipitate, flocculation, turbidity or opacity, as appropriate [14] . The presence or absence of any of the above constituents in the tested extracts was determined according to the type of chemical reaction in the presence of an appropriate reagent. The test is negative (-) when there is no active compound in the extract. This absence is confirmed by no change in colour or no formation of a precipitate. The reaction is considered weakly positive (+) when there is slight opacity or low-intensity colouring followed by weak precipitation. On the other hand, the reaction is moderately positive (++) in the case of marked turbidity or distinct colouring. Finally, the test result is considered strongly positive (+++) when there is strong precipitation, flocculation or intense colouring.

Statistical analysis

Data on the primary and secondary metabolites and mineral content of five organs from four species of wild edible plants, analysed in triplicate, were subjected to analysis of variance (ANOVA) using PAST and SPSS v27.0. In cases of significant differences between varieties, comparisons of means were performed using Duncan’s test. Decisions were made at a significance level of 5% (p < 0.05).

Table 1 shows the average content for each physicochemical parameter of the organs of plant species analyzed.

The are differences in average means for the independent samples. For matched samples, the single sample T-test Protein-carbohydrates (t = −1.429, p = 0.226), indicates no difference. However, the comparison between Protein-Lipids in the samples (t = 9.139, p < 0.001), indicates a significant difference, therefore samples are richer in protein than in lipids. The same for carbohydrates-lipids (t = 5.387, p = 0.006), significant difference has been observed, therefore samples are richer in carbohydrates than in lipids.

The following table shows the results of chemical analysis of the mineral matter in the different samples.

There is a significant difference between the average means of all minerals in the selected sample plant species (p < 0.001).

The following table summarizes the results of qualitative phytochemical analysis of ten secondary metabolites in the leaves of the different samples ( Table 3 ).

Key: +++: Strongly positive test; ++: Moderately positive test; +: Weakly positive test; -: Negative test.