INTRODUCTION

Plants (wild and cultivated) are the base of the terrestrial food chain and are consumed daily all over the world. According to Dupriez and Leener (1993), plants are essential natural resources for human nutrition and care. The designation “wild plants” refers to non-cultivated plants gathered from wild and agricultural landscapes (Termote, Bwama, Dhed’a, Huybregts, & Lachat, 2012). WFPs have been part of diets and traditional food systems throughout human history, providing important nutrients and bioactive compounds. Ancestral and contemporary traditional diets are known to offer valuable health benefits (Crittenden & Schnorr, 2017). WFPs are traditional foods that tend to be richer in micronutrients than cultivated crops (Hunter et al., 2019; Mawunu et al., 2020; Zinöcker & Lindseth, 2018). WFPs are embedded in traditional food knowledge, which represents an integral part of local and sovereign the food systems (Abdul, Abbasi, Ullah, & Pieroni, 2020). Despite their potential benefits, WFPs have been overlooked and excluded from most formal education, policies and research or development programs. The barriers to a greater use of WFPs were reviewed by Heywood (1999), with the main ones being a lack of information, statistics, market infrastructure, research and policies. Moreover, food and agriculture sectors have neglected wild species in favor of cash crops and starchy staples (Bharucha & Pretty, 2010). In addition, their free availability in nature has resulted in low economic valuation, which further reduces their visibility and promotion despite their nutritional, health, social and ecological benefits (Ngome, Shackleton, Degrande, & Tieguhong, 2017) and economical.

In traditional societies around the world, knowledge has always been or is still transmitted orally. Angola is no exception to this reality. The history of Angola is essentially marked by oral tradition, so ethnobotanical records are scarce. However, there are some more recent studies that clearly demonstrate that the practice of using native and exotic plants to cure diseases and for food is a very old practice among people. Even so, the high lack of written records can be understood since people pass on their teachings to younger people through orality (Heinze et al., 2017).

Several ethnobotanical investigations have been undertaken in northern Angola to document and thus perpetuate traditional knowledge such those linked to wild medicinal and food plants. The literature of these investigations include the works of Alexandre (2019); Jendras, Monizi, Neinhuis, and Lautenschläger (2020); Lautenschläger et al. (2018); Lautenschläger et al. (2020); Lautenschläger, Mandombe, Mawunu, and Neinhuis (2020); Mawunu et al. (2016); Mawunu et al. (2018); Mawunu et al. (2021); Mazekana and Carlos (2019); Monizi et al. (2018), and Göhre, Toto-Nienguesse, Futuro, Neinhuis, and Lautenschläger (2016). In this context, the current study aims to document the traditional knowledge of wild food plants consumed by the villagers of Mucaba municipality.

MATERIAL AND METHODS

Location and characterization of the study area

Mucaba is one of the 16 municipalities of Uíge province located 60 km north of the provincial capital Uíge. It covers a land area of 964 km2 and a population of 43,974 inhabitantsFigure 1 (NIS, 2014) .

Mucaba municipality location

Mucaba is located almost in the center of Uíge province. It is bordered by Damba municipality to the north, Bungo municipality to the east, Bembe and Songo municipalities to the west and Uíge municipality to the south. The population of Mucaba municipality is originally Bantu from Bakongo ethnolinguistic group. The origin of the name Mucaba, derives from the river "Nkamba" (in kikongo language), which means safety belt (, 2012). Mucaba is a municipality with an eminent agricultural profile. The traditional agricultural calendar is divided into three seasons. The first agricultural season, locally called as Ntema or Masanza runs from October to February of each year, while the second season, locally called Kintombo, runs from February to June. Finally, the third season, locally called Mulenga or Mbangala, runs from July to September. Subsistence agriculture is the main source of income, food diversification and social stabilization. The main agricultural products are cassava, bananas, groundnuts, sweet potatoes, coffee, beans, yams (Quissadi), maize and squash (Personal communication).

As for the climate aspects, Mucaba fits into a tropical hot and humid climate region with two well-defined seasons namely the dry season or Cacimbo from mid-May to August [Sivu ou Mbangala in Kikongo language] (Mawunu et al., 2016) and the rainy season corresponding to the remaining period of the year. The dry season is characterized by practically zero precipitation, but the dryness of the air and evaporation are mitigated by high relative humidity, cloudiness, and both persistent and frequent fogs. During Cacimbo season, night dew is almost a daily occurrence, with greater incidence in the early hours of the morning, and sometimes even small amounts of precipitation. Mucaba registers an average rainfall value of 900 mm in the western border and reaches up to 1500 mm in the interior. In the rain distribution there are two rainfall peaks in (November and April) separated by a short period without rain that takes place in January or February.

The average annual relative humidity at 9 o'clock is above 80%, while the coldest months are July and August, with average minimum values of 13oC and 14oC (Diniz, 2006).

Plant Materials

The plant material referred to in this research consists of the samples of wild food plants collected in Mucaba municipality. The field work was carried out over a period of approximately two months (September and October of 2020). The names of plant families were listed in alphabetic order. For the listing of taxa, we followed the APG (Group, et al., 2009). We checked the spelling of the scientific names using the base according to the plant list. (http://www.theplantlist.org, accessed on 10/October/2021). Finally, both the teachers and the researchers of Kimpa Vita University have carried out the scientific identification of the species.

Study methodology

Harvested plant habitats

The different ecological environments that host the edible wild plant species of Mucaba are presented in Figure 2.

Distribution of wild food plants by habitat (%)

The results in Figure 2 show that forest (52%) and savannah (34%) are the habitats par excellence of wild food plants in Mucaba. The remaining plants were found in the fallows (10%) and ploughs (2%). Mawunu et al. (2016), pointed out that in Ambuila Municipality 72 % of wild food plants are from forest, 25 % from savannah and 3 % of species are ubiquitous (belong in both habitats). In contrast, (Mazekana et al., 2019) reported that the majority (37%) of wild food plants in Uíge Province are from savannah, 34 % are from forest and more than a quarter (29%) are ubiquitous (forest and savannah). Several reasons may be behind these observations, since Uíge province is made up of several agro-ecological zones and different microclimates and ecosystems. The study by (Mazekana et al., 2019) covered almost all the agroecological zones of Uíge province and covered the two main seasons of the region (dry and rainy) which is why more species were found as compared toMawunu et al. (2016) and Alexandre (2019).

Morphological form

Figure 3 shows the morphological form of the different wild food plants surveyed from the Mucaba.

Morphological type of edible wild plants (%).

The wild food flora of Mucaba Municipality is richly dominated by herbaceous (38%) and trees (24%). This is followed by shrubs (22%) and climbers (16%). The results of this research corroborate with (Mazekana et al., 2019), who reported that herbaceous predominate (37%) the wild food species in the entire Uíge province. This is followed by shrubs (23%), climbers (21%) and trees (19%). Mawunu et al. (2016) in Ambuila Municipality also reported predominance of herbaceous (34 %) and trees (32 %). Climbers and shrubs occupy 25 % and 9 % respectively.

The differences observed in this item with previous studies byMawunu et al. (2016) and (Mazekana et al., 2019) would be linked to the availability of guide-informants, accessibility of the sampling areas and the state of degradation of ecosystems due to anthropic activities.

Edible parts

Figure 4 shows the food parts of the wild plants investigated at Mucaba.

Parts of wild food plants used (%).

The data in Figure 4 show that leaves (47%) and fruits (37%) are the most abundant edible wild plant organs in the Mucaba. In addition, saps and seeds each have 5%. The other organs (7%) of plants consumed are root bark, stem bark (Mondia whitei) and tubers (Dioscorea praehensilis). Consumption of inflorescences was observed in only one species, Lippia multiflora (Bulukutu). The inflorescences of L. multiflora are boiled and consumed as tisane (Tea substitute). The other species consumed in this municipality presenting also one or two organs are Raphia sp. (the sap and fruits), Pteridium centrali-africanum (the shoot), Vitex mandiensis (fruits and bark), Costus afer (the stem) and Dioscorea praehensilis (the tuber). According to Mawunu et al. (2016) fruits and seeds (45%) and leaves (33 %) are the most abundant edible plant organs of wild plants in Ambuila. (Mazekana et al., 2019) , also reported that fruits (57%) and leaves (31%) are the main edible organs of wild plants in Uíge province. On the other hand, the fact that fruits are more representative than other edible plant organs this shows a conservation character of the plant resource, because it does not prevent the development and reproduction of the plant (Martin, 1995), as well as the consumption of seeds and leaves if the removal of the aerial part is not excessive (Pilla, De, Amorozo, & De, 2009) .

Modes of preparation and consumption

Harvested plant organs are consumed in various ways. This also explains the different ways or modes of preparation. The leaves are all used in the preparation of sauces, except for L. multiflora, whose leaves are used in the preparation of herbal tea. All these leaves are therefore cooked before consumption. As for the fruits, some can be eaten directly without any form of treatment, such as Aframomum alboviolaceum, Aframomum stanfieldii, Aframomum angustifolium, V. madiensis, V. ferruginea and Syzygium guineense var. littorale. In addition, other seasonal fruits undergo thermal treatments, such as boiling, as in the case of Canarium schweinfurtii. In some species, the mucilage or pulp around the seeds can be consumed directly, as in the case of Adansonia digitata (Nkondo or Imbodeiro in the local languages), where mealy pulp is eaten raw or made into juice after boiling or soaking in water at room temperature. Note that the seeds are used to enhance the flavour of food (spices). They are also used whole or crushed to give a seasoning used in the preparation of sauces or sprinkled on meat, chicken or fish before they are butchered, Monodora myristica (Mpeve in the local Kikongo language), Piper guineense (Kumpi or Kampidi in the local Kikongo language) and Xylopia aethiopica (Nkuwa nkuwa in the local Kikongo language). For Raphia species, the sap is used as a popular local drink (Raphia wine, commonly called Matombe or Maruvo) because of its cultural value, while the Raphia fruit (Nkulu in the local Kikongo language) can be eaten raw to ease stomach pains or cooked to extract. Finally, the barks of two species, V. madiensis (stem and root bark) and M. whitei (root bark) are used as tea and stimulant (aphrodisiac) respectively. As for the frequency of consumption of wild food plants, the study revealed that on average, 51% of the interviewed households consume them once a month, 27% consume them annually and 22% consume them once a week. On the other hand, wild food plants are consumed by children, youth, adults and elders. Some plants such as A. alboviolaceum, A. stanfieldii, A. angustifolium and Landolphia owariensis, which are a little acidic are preferred by one or two categories of people, children and women, especially pregnant ones. G. africanum leaves are much appreciated by adults, men and women because of their cultural value as local products. Finally, M. whitei roots are much consumed by men for their alleged aphrodisiac virtue.

Ways of acquiring food edible wild plants

Figure 5 shows the ways in which wild food plants are acquired in the Mucaba.

Forms of harvesting the wild food plants.

The results in Figure 5 show that fruit picking (48%) and defoliation (37%) are the main techniques used by Mucaba villagers in obtaining wild food plant organs. Other techniques used were: uprooting (11%), peeling (3%) and tree felling (1%). These last three techniques are not sustainable because they can cause a genetic erosion of the edible wild flora.Mawunu et al. (2016) revealed that harvesting (58%) were the most commonly used techniques in the acquisition of wild food plants in Ambuila. The other techniques reported were felling (11%) and shelling with 4%. Monizi, André, Luyeye, Ngbolua, and Luyindula (2019), reported that in the gathering of Dracaena camerooniana leaves, the hunter-gatherers pick the leaves and sometimes cut the whole plant.

Other uses of the wild food plants investigated

Figure 6 shows the other uses of wild food plants in Mucaba.

Other uses of wild food plants in Mucaba (%).

The results in Figure 6 show the non-food uses of inventoried plants. Mostly, wild food plants are used as traditional medicine (32%), bioenergy (firewood, 24%; charcoal, 12%) and construction material (22%). In addition, 12% of the food plants are used in charcoal making. Finally, other wild food plants are used by Mucaba villagers in handicrafts (7%) and as stimulants or aphrodisiacs (2%).

Acquisition and transmission of knowledge

The results of this study show that traditional knowledge comes from relatives or older people in the community. As for its transmission it is done according to the oral tradition of the region, a millennial means of preserving the know-how. Authors such as Monizi et al. (2018), Mawunu et al. (2018) andHeinze et al. (2017) reported similar results regarding the transmission of traditional knowledge in northern Angola.

Socio-economic value of some wild food species

Some wild food species inventoried in Mucaba are usually traded locally by women and children. Among these species are those whose seasonal fruits, leaves, sap, shoots, seeds or grains are sold in local markets in their entirety: A. alboviolaceum, A. angustifolium, A. stanfieldii, S. cocculoides, P. guineense, X. aethiopica, C. schweinfurtii, M. myristica, L. owariensis, Raphia spp, P. Centrali-africanum, G. africanum and M. whitei.

Concerning the organs of wild food plants sold in Mucaba, the leaves of G. africanum in bundles are the most expensive (0.75 US$) while the fruits of Aframomum are the most affordable costing on average 0.17 US$, a bunch.

The research conducted byMawunu et al. (2016) in Ambuila municipality, inventoried 10 wild food plants sold in Ambuila Municipality. Among them, P. guinneense (Kumpidi in the local Kikongo language), G. africanum (Mfumbwa in the local Kikongo language), C. acuminata (Makazu in the local Kikongo language), L. multiflora (Bulukutu in the local Kikongo language) and Raphia spp. (Matombe or maruvu). Mawunu et al. (2020) also made an inventory of 35 wild food plant species sold at the markets of Uíge province. These are: A. digitata, A. alboviolaceum, A. angustifolium, A. stanfieldii, Anisophyllea quangensis, C. schweinfurtii, C. acuminata, Cucumis metuliferus, Crassocephalum montuosum, C. rubens, Cymbopogon densiflorus, Dacryodes edulis, Dracaena camerooniana, Erythrina abyssinica, G. africanum, L. multiflora, Landolphia lecomtei, L. lanceolata, L. owariensis, M. whitei, Monodora angolensis, Ochna afzelii subsp. mechowiana, P. guieneense, Plukenetia conophora, Pteridium aquilinum subsp. Africanum, Pterocarpus angolensis, Raphia spp, Salacia pynaertii, Scrodophloeus zenkeri, S. cocculoides, S. guineense subsp. Macrocarpum, Treculia africana and X. aethiopica.

The results of this study show that the majority (62%) of wild food plants in Mucaba are sold at the markets. In addition, the other places of sale are the homes of the harvesters (25 %) and roadside (13 %). Mawunu et al. (2020) and Monizi et al. (2018); Monizi et al. (2019) found similar results.

We point out that vendors use various non-standardized selling instruments and modes. The instruments and modes of sale depend on the physical state of the products, solid or liquid. Sale in heap is the main mode (69%), followed by sales in liter, bowl and tin (locally called kilogram) which occupy 13%, 12% and 6% respectively. According to Mawunu et al. (2020), for example, Mucua (A. digitata) pulp is sold in bunch, bucket or 50-150 kg bags. Likewise, fruits and bark are sold in bunch, tub, bucket and tin. Liquid edible non-wood forest products (maruvo, palm oil, etc.) are sold in liters. Finally, leafy vegetables like Mfumbwa (G. africanum), Mbonde (S. pynaertii), Nlondo londo (M. whitei), and tisane (Tea substitute): Buluku (L. multiflora), Kikaya or Kimbele tea (Uvariodendron molundense), etc., are sold in bundles.

Destination of income

The results of this study show that most (78 %) of the money earned from the sale of wild food plants in Mucaba is used to buy basic necessities. Only 19 % of the money is used to buy school materials. Finally, 3% of the money is used for other purposes such as health, agricultural materials, food and clothes. The results of this study partially corroborate the studies of Monizi et al. (2018); Monizi et al. (2019), which reported that income from the sale of non-mandated forest products (food and non-food) contributes to the strengthening of food security and acquisition of both goods and services (purchase of school supplies, health care, basic necessities, contributions in deaths and marriages, church).

Constraints and Importance of Sustainable Resource Management

The abundance of wild food plants in Uíge province, specifically in Mucaba municipality is constantly threatened by anthropic activities. These threats may contribute to the genetic erosion of plant biodiversity in particular and biological biodiversity in general. The main anthropic activities observed are: subsistence agriculture and the use of non-ecologically unsustainable harvesting methods by some gatherers, such as felling, uprooting and peeling. Finally, except for C. acuminata, the harvesting of other wild food plants is done freely without prior authorization from the government bodies.

CONCLUSION AND SUGGESTIONS

An ethnobotanical study on wild edible plants was conducted in Mucaba municipality, northern Angola. A total of 46 wild edible plants and their traditional uses were documented in this study. Our results show that Mucaba people have plentiful traditional knowledge on the utilization of wild edible plants with diversified eating parts, consumption methods, and use purposes. By building on the traditional knowledge of Mucaba villagers and encouraging them to diversify the cultivation of wild edible plants on the fields, as well as in their home gardens, a new bridge could be built for wild plants to become more profitable cash crops, contributing to their sustainable use and preserving the endangered species in this region. A policy of sustainable natural resources management can be created to integrate social, cultural and economic values of local communities.

Conflicts of interest

The authors declare no conflict of interest.

Author contributions

MM, TL- Research concept and design, MM, MHGP- Collection and/or assembly of data, MM, AT, KNN–Data analysis and interpretation, MM, KNN- Writing the article, MM, LN, LL, KNN–Critical revision of the article. All authors have read and approved the manuscript.