Socio-demographic and ethnobotanical surveys

The survey was conducted between May and August 2022. A total of 250 randomly selected informants were interviewed, including 152 female (62.02%) and 98 (37.98%) men, all residents of the study area, and at least 18 years of age. The informants were chosen at random, in order to give everyone the same chance, without favouritism. The interviews were oral, but there were also written forms. These informants were approached using semi-structured interviews that were conducted in the Portuguese language. Semi-structured interviews and direct field observations were used to collect ethnobotanical data (Lautenschläger et al., 2018; Mawunu et al., 2022; Mawunu et al., 2023; Mawunu et al., 2023), and based on the open-ended interview guide, which avoids influencing the informant's response (Martin, 2004).

Questionnaire

The questionnaire was divided into two sections: (1) attributes of the personal informant (including, gender, age, education level, and source of income); and (2) ethnomedicines data (including, local names of medicinal plants, habitat, life forms, and the status of medicinal plants used, plant organs used, ailments treated, and in each case the methods of preparation and administration were also recorded (Mawunu et al., 2022). During the fieldwork, plant samples were collected, and photographs were taken for later identification. The individual anthropological interviews were conducted in the local languages Kikongo and Portuguese, the languages spoken by the informants. It should be noted that some of the informants interviewed spoke all three languages, while others spoke only one. For this reason, during the interview, the informant was questioned in the language he or she spoke best. Besides, the selection criteria of the surveyed people were based on the age of informants (aged 18 years old and over) who had knowledge of the utilization of medicinal plants under investigation anwd uses of those plants in the management of human diseases, and who were available at the time of the survey. At last, direct observations and the semi-structured questionnaire were submitted orally to the different informants (18-80 years old).

Identification, classification and ecological characterization of the plants studied

Scientific names have been updated in accordance with the Plants of the World Online database (POWO, 2023). This database originates from the Royal Botanic Gardens (Kew) and all taxonomic data incorporated reflect the latest peer-reviewed studies on accepted scientific names and synonyms of plant families. In addition, the life forms of the species listed have been classified using Raunkiar's life form classification method (Raunkiaer, 1934). The inventoried plant species are classified into different morphological types based on the Raunkiaer system (Raunkiaer, 1934), as adopted by Lejoly, Lisowskis, and Ndjele (1988), and Pisco et al. (2024). These types include trees (over 15 m in height), shrubs (under 7 m), small shrubs (under 2 m), lianas (climbing plants), and annual herbs (plants whose aerial and underground parts die each year). Biological types are also classified using the Raunkiaer system, extended to tropical areas. These types are geophytes (plants with buds and young leaves in the soil), therophytes (plants that persist as seeds during unfavorable seasons), caephytes (plants with small vegetative devices and persistent leaves), and phanerophytes (plants with aerial sleeping buds over 50 cm above the soil). Phanerophytes include mesophanerophytes (10-30 m tall), microphanerophytes (2-10 m tall), nanophanerophytes (0.4-2 m tall), and lynephanerophytes (woody, climbing plants). The biotope types are determined from existing floras and include primary forests, secondary forests, savannahs, ruderal areas, and cultivated species. The phytogeographical distribution is determined using the classification of (Mawunu et al., 2024) , based on criteria such as widely distributed species (e.g., cosmopolitan, pantropical, afro-neotropical, palaeotropical), widely distributed African species (e.g., Afro-tropical continental, Afro-Malagasy), and regional species (e.g., Sudanese, Guinean-Congolese, Zambezi).

Data processing and analysis

Data processing and analysis uses Microsoft Excel 2010, IBM SPSS Statistics 20 and Origin. Briefly, the data collected was first in put into Microsoft Excel and analysed using IBM SPSS statistics. A single-variable analysis of categorical variables (socio-demographic and ethnobotanical variables) was conducted to obtain descriptive statistics including relative frequencies. The Kolmogorov-Smirnov test is used to verify the normal distribution of quantitative variables. Multivariate analysis, in particular multi-correspondence analysis, is carried out to investigate the relationship between dependente variables (ethnological parameters) and independent variables (socio-demographic parameters). Additionally, it should be noted that the Kolmogorov-Smirnov test was used to validate the hypotheses concerning the distribution of data on the age of the respondents, while Multivariate analysis was used to analyse and visualise the relationships between qualitative variables, thus enriching the analysis of ethnobotanical practices and knowledge.

Three types of frequencies were determined in order to provide analytical support for the taxa inventoried during the survey work: Relative frequency of Citation (RFC), citation index (CI), and medicinal capability index (MCI):

(1) Relative frequency of Citation (RFC), this index presents the number of informants who mention the use of the species (FC) in the number of informants participating in the survey (N) (Shuaib et al., 2021), and the Relative frequency of citation (RFC) index shows the local importance of each species;

The following Formula 2 calculates the index: RFC= FC/ N. The RFC index varies from 0 to 1. An RFC index of 0, means that nobody refers to the plant as useful, but an RFC index 1 indicates that all informants in the survey agreed that this plant is useful. FC: Citation frequency is the number of informants who mentioned a particular species and N: Total number of informants. As well, the relative frequency of citation index in percentage (FRC%) was calculated as follows number of reports of use (number of times a particular species was mentioned) / (Total number of times all species were mentioned) × 100 (FRC%) and was used as a quantitative index. Moreover, in ethnobotanical study, RFC indicates the native significance of plants species present within a region (Umair, Altaf, & Abbasi, 2017) .

(2) Confirmation Index or Informant Consensus (CI or ICs), IC = NP/NT. In this formula, NP is the number of informants who cited a species; while NT is the total number of informants. The ICs varies between [0 - 1]. A low value, close to 0, indicates that the informants disagree on the proposed uses. When this value is close to 1, it indicates high agreement around the use of the plant. ICs: the Informant consensus of use (ICs) was calculated to assess the agreements of informants on the use of plants for therapeutic uses (Byg & Balslev, 2001). Besides, this index makes it possible to evaluate the local cultural importance of a medicinal plant cited by different surveys in a given territory. For example, in this study the CI allows us to determine the number of times a plant has been cited in the management of hemorrhoids in the region, and consequently to identify the level of consensus within the population on the curative use of a given species in the management of hemorrhoids.

(3) The medicinal capability índex (MCI), was calcuted by the formula MCI= Number of taxa cited to manage a give pathology/Total number of taxa inventoried during the study. Besides, the MCI enables us to measure the potential of a given community to manage a well-dened pathology (Valentin et al., 2024).

Life forms, status of origin and habitats of the plants studied

Figure 2 shows the morphological shape of plants documented in the Kimalalu.

Figure 2

Growth forms of the plants studied (%).

The study showed that the most frequently cited life form was shrubs with 22 species (30.99%), followed by trees (16 species, i.e. 22.54%), sub-shrubs (15 species, i.e. 21.13%) and herbs with 12 species (16.90%), including 7 species of perennial herbs (9.86%), 5 species of annual plants (7.04%) and 6 species of lianas with 8.45% (Figure 2). Shrubs are the most commonly used plant species in the study area. This could be due to their abundance and accessibility in the region and the abundance of associated knowledge within the community. This study relates wiith Mawunu et al. (2022), where dominance of shrubs in the medicinal flora of the Songo, Angola.

In contrast,Lautenschläger et al. (2018) in their first large-scale ethnobotanical study in the province of Uíge, northern Angola, reported that trees were in the majority compared to other life forms. Additionally, with regard to the status of origin of the medicinal plants recorded in this study, the majority were indigenous species (41 species, i.e. 57.75%) while the remainder (30 species, i.e. 40.25%) were of exotic or introduced (allochthonous) origin. Lastly, of all the medicinal plants (72 species) collected and identified in the study area, the majority (29.9%) came from allotments in the vicinity of dwellings. The other medicinal plant harvesting sites were savannah (21%), fallow land (18.6%), forest (16.8%) and cultivated fields (13.6%). (Mawunu et al., 2022) who studied the medicinal flora of the small town of Songo reported that the greater part (67.4%) of medicinal plants were of exotic origin. With regard to habitat,Lautenschläger et al. (2018) also reported that the majority of medicinal plants grew in savannahs and forests.

Parts of plants used in the preparation of phytoremedes

Figure 3 shows the different parts of plants used to treat human diseases in the study area.

Figure 3

Parts of medicinal plants used in the Kimalalu flora (%).

Medicinal preparations were made from a single part of the plant or a combination of several plant parts. Figure 3 shows that the leaf was the part of the plant most commonly used to make phytomedicines in Kimalalu (53.05%), followed by roots and root bark (14.32%), inflorescences (7.43%), stem and stem bark (7.17%), seeds (2.65%), fruit and fruit pulp (3.45%), tubers (0.27%) and sap with 0.27% (Figure 3). The use of leaves as compared to roots is considered less destructive especially to trees and shrubs. It is important to note that, in some species, more than one part was used in the preparation of phytomedicines. Leaves were the dominant plant parts employed in remedy preparations for the treatment of human in the study area, which could be attributed to their perceived efficacy, accessibility, ease of harvesting, and simplicity of preparation. Our results are in line with the conclusions of similar studies carried out in Angola and elsewhere in the world (Abadi, Neinhuis, Safaeian, & Lautenschläger, 2023; Camacho-Hernández, Lagunez-Rivera, Aguilar-Contreras, & Gómez, 2022; Djoza et al., 2021; Lautenschläger et al., 2018; Liyongo et al., 2023; Mawunu et al., 2022; Mobale et al., 2023; Pisco et al., 2024) in which the most widely used part of the plant was also the leaves, used to treat various human ailments.

Also, the preference for leaves for medicinal production is a positive result for the conservation of plant resources. Collecting leaves in moderation neither harms nor affects the health, reproduction or development of the plant. This practice is linked to the abundance and convenience of using leaves compared to other parts of the plant, as well as to confidence in the effectiveness of its use (Santos, Amorozo, & Ming, 2008). Lastly, harvesting leaves has been reported to have much less damaging effects on the mother plant as compared to other parts such as roots and barks, the gathering of which could seriously affect the existence of individual plants (Teka, Asfaw, Demissew, & Damme, 2020).

Biological types

Data on the biological types of the flowering plant studied are shown in Figure 4 .

Figure 4

Biological types of documented plants (%).

The biological types show a predominance (Figure 4) of Phanerophytes with 45 species, i.e. 62.54% of the flora inventoried; followed by Therophytes with 12 species, i.e. 16.67%; Geophytes with 6 species, i.e. 8.34%; Chamaephytes with 6 species, i.e. 8.34% and Hemicryptophytes with 3 species, i.e. 4.17% of the flora studied. This predominance of Phanerophytes gives a forest-like appearance to the flora studied. Among the Phanerophytes, mesophanerophytes (MsPh) are the most preponderant with 21 species, i.e. 29.17% of the flora, followed by microphanerophytes (McPh) with 13 species, i.e. 18.06%; nanophanerophytes (NPh) with 9 species, i.e. 12.50%; and creeping phanerophytes (CPh) with 2 species, i.e. 2.78% of the flora. Cryptophytes include rhizomatous geophytes (Grh) with 4 species (5.56%) and tuberous geophytes (Gt) with 1 species (1.39%). Within the Therophytes, there are erect therophytes (The) with 8 species, i.e. 11.11%, climbing therophytes (Thc) with 3 species, i.e. 4.17% and prostrate therophytes (Thpr) with 1 species, i.e. 1.391%. In the Chamaephytes, we distinguish the erect chamaephytes (Che) with 5 species, i.e. 6.94% and the rhizomatous chamaephytes (Chrh) with 1 species, i.e. 1.39% of the flora studied. Lastly, there are the Hemicryptophytes (Hce), with only 3 species, or 4.17% of the flora inventoried. The abundance of phanerophytes proves the forested nature of the study site. The present results are in agreement with previous studies carried out in the same region by (Mawunu et al., 2023), who reported that the dominance of phanerophytes (52.2%) in the ethnobotanical survey of herbal teas consumed in the province of Uíge (Angola) reflects the state of vegetation in the tropics. These results corroborate those of research carried out on the flora of the Wamba valley in the DRC (Théophane et al., 2022).

Phytogeographical distribution of documented plants

Table 3 shows the phytogeographical distribution of the flora studied in the Kimalalu community in the Uíge province.

Table 3 shows that the proportion of species with a very wide distribution (51.39%) and African species with a wide distribution (41.67%) are the most important in the flora studied. The largest of the medicinal flora studied is made up of tropical species with 68.05% (Table 3), including 29 pantropical species representing 40.28% of the total and 15 Afro-tropical species, i.e. 20.83%. Paleotropical species followed (5/72, i.e. 6.94%), Lower-Guineo-Congolese (2/72, i.e. 2.78%), and Afro-Malagasy (2/72, i.e. 2.78%). Also, the Afro-American, Cosmopolitan, Guineo-Congolese-Zambezian, Guineo-Congolese-Sudanese and Guineo-Congolese-Sudanese-Zambezian species each have 1 species with 1.39% (1/72). The present results are in agreement with the previous study carried out in northern Angola by (Mawunu et al., 2023). These results corroborate research carried out in the DRC by Théophane et al. (2022), Masengo et al. (2024).

Types of foliar dimensions

The overall analysis of the types of leaf dimensions of all the species inventoried in the Kimalalu is illustrated in Figure 5.

Figure 5

Types of foliar dimensions of the flora studied (%).

Figure 5 shows that mesophyll species are more numerous; they make up 41 species, or 56.94% of the total number of plants in the flowering bed. Microphylls accounted for 21 species (29.17%), nanophylls for 5 species (6.94%), macrophylls for 4 species (5.56%) and leptophylls for 1 species (1.39%). Similar results were also reported by Théophane et al. (2022), andPisco et al. (2024) in the DRC.

Types of diaspora

Analysis of diaspora types produced the results shown in Figure 6.

Figure 6

Types of diaspores in the flora studied (%).

Analysis of the spectra of diaspores highlights the clear dominance (Figure 6) of Zoochores with 35 species, i.e. 48.61% of the florule inventoried. These types of diaspores are spread by animals (Zoochory). Anemochores followed with 19 species (26.39%); Autochores (Ballochores) with 17 species (23.61%); and Barochores (Baro) with 1 species (1.39%). Among the Zoochores, the Sarcochores (Sarco) are the most dominant with 33 species, i.e. 45.83% of the florule studied and 94.29% of all the Zoochores in the florule inventoried; then come the Desmochores (Desm) with 2 species, i.e. 2.78% of the florule inventoried and 5.71% of all the Zoochores in the florule studied. Among the Anemochores, we find Sclerochores with 10 species, i.e. 13.89% of the flora inventoried and 52.63% of all the Anemochores in the flora studied; Pterochores with 3 species, i.e. 4.17% of the florule inventoried and 15.79% of all the Anemochores and Pogonochores with 6 species, i.e. 8.33% and 31.58% of all the Anemochores in the florule inventoried. Similar results were reported byThéophane et al. (2022) in their study of the flora of the Wamba valley in the DRC.

Solvents and methods used in the preparation of phytomedicaments

It should be noted that the informants used several solvents when preparing the phytomedicines, in particular water (96.6%), palm wine (2.4%) and honey (1.2%). Furthemore, some remedies were prepared without the additional solvents mentioned above.

Methods of preparing phytoremedias

Figure 7 shows the different methods of preparing phytoremedias used by the Kimalalu communities.

Figure 7

Preparation methods for medicinal plants used to treat human ailment (%).

Various traditional methods of preparing phytomedicines were used in the study area (Figure 7). The preparation method most commonly used to treat human diseases was decoction (50.00%). The other preparation methods used to make phytomedicines were maceration (22.75%), grinding (12.57%), mastication (6.89%), cooking (2.78%), pressing (1.80%), root cutting (1.50%), roasting (2.10%), cooking (1.20%), heating (0.60%), peeling (0.30%) and incision (0.30%) (Figure 7). The common practice of decoction as a method of preparing medicinal plants can be explained by the fact that it is an easy way to collect the main medicinally active compounds (active ingredients) and to attenuate or eliminate toxic substances present in some medicinal plants (Lazli, Moncef, Ghouri, & Nouri, 2019). Also, Li et al. (2024), reported that decoction is generally considered the most common method of herbal medicine preparation because it can easily and effectively extract the active ingredients from the plant materials. Similar results have been reported by authors such asLautenschläger et al. (2018) and (Mawunu et al., 2022) in Angola, (Ngbolua et al., 2021) in DRC, andMoncayo and Diago (2022) in Colombia that decoction is the main preparation method in traditional therapeutic recipes. Furthermore, the study byCanga et al. (2022) showed that the use of maceration to prepare a remedy was the most frequently used preparation method.

Phytoremediation routes

With respect to the routes of remedy administration, the local community recommends different routes depending on the type of disease treated. Figure 8 shows the different methods of administration used by the Kimalalu communities.

Figure 8

Phytoremediation methods (%).

There are different ways of administering the traditional medicinal products prepared by the local community of Kimalalu. Seventeen (17) methods of administering herbal treatments are used by the Kimalalu communities in northern Angola (Figure 8). The most frequently used route of administration is oral (56.21%), followed by cutaneous topical (12.13%), mouthwash (6.8%), enema (6.51%), inhalation (3.55%), eating (4.73%), bath (3.85%), steam bath (2.07%) and eyewash with 1.48% (Figure 8). Other methods of administering phytomedicines (tying on the head, ear drops, face wash, nasal drops, etc.) accounted for 2.66%. Oral was the most popular route of remedy administration which could be due to the reason that it creates favorable environmental condition for quick physiological reaction of the preparation against the pathogens and by so doing boosts its healing power. Oral administration has an additional advantage in that it allows the traditional medicine practitioners to reverse complication that might happen on the clients during treatment using antidotes. The results of this study are in agreement with other studies such as Mawunu et al. (2022); Pisco et al. (2024), and Lautenschläger et al. (2018) who reported that the oral route of administration (per os) is the most commonly used in Northern Angola.

The frequent use of oral absorption as a route of administration for medicinal plants may be related to the fact that it is rapid and provides a large effective surface area for absorption of the active drug components (Hillery, Lloyd, & Swarbrick, 2001). Oral administration has an additional advantage in that it allows the traditional medicine practitioners to reverse complication that might happen on the clients during treatment using antidotes. Once absorbed, the drug passes through the intestinal wall and liver before being transported to target sites via the bloodstream (Kwon, 2005).

Diseases and symptoms treated by phytotherapy

The study identified 59 human symptoms and illnesses treated with phytomedicines by the inhabitants of Kimalalu. Figure 9 shows the diseases and symptoms treated with medicinal plants, highlighting the sixteen main illnesses documented in the study area.

Figure 9

Main diseases and symptoms documented at Kimalalu (%).

According to the data in Figure 9, the condition that most affected Kimalalu residents during the ethnobotanical surveys was low haemoglobin (12.53%) - commonly known as anaemia. This was followed by yellow fever (6.04%), abdominal pain (5.59%), toothache (5.37%), cough (4.70%), typhoid fever (4.25%), fever (4.25%), malaise (4, 25%) and diarrhoea (4.25%), malaria (3.36%), lordosis (2.91%), diabetes (2.91%), colds (2.91%), asthma (2.91%), inflammation (2.46%) and gastritis (2.24%). Studies by (Mawunu et al., 2022) reported that in the small town of Songo, medicinal plants were used more for the treatment of coughs, anaemia, malaria and diarrhoea. Besides,Canga et al. (2022) reported the dominance of infectious and parasitic diseases, notably malaria, leprosy and cholera. Further, (Pathy, NB, BK, W, & P, 2021) in the city of Mbanza Ngungu in the DRC reported that haemorrhoids, hernia and sexual impotence were the most prevalent diseases.

Frenquency of citation

The current study is the first report on medicinal plants used in traditional medicine in Kimalalu, northern of Angola. Table 6 shows the different citation frequencies of the medicinal plant species in the current study, i.e. frequency of citation (FC), relative frequency of citation (RFC), relative frequency of citation in percent (RFC%) and CI is used to determine the number of times a plant has been cited in the management of diseases in the study area.

According to the results in Table 6, the highest relative frequency of citation (RFC) was observed in Persea americana with RFC=0.04, followed by Harungana madagascariensis (RFC=0.037), Spondias mombin (RFC=0.037), Dysphania ambrosioides (RFC=0.034), Senna occidentalis (RFC=0.031), Securidaca longepedunculata (RFC=0.028), Entada abyssinica (RFC=0.025), Pachylobus edulis (0.028), Securidaca longepedunculata (RFC=0.028), Ficus sycomorus (RFC=0.025), Mondia whitei (RFC=0.025), Cymbopogon densiflorus (RFC=0.022), Indigofera paracapitata (RFC=0.022), Ocimum gratissimum (RFC=0.022), Pleiotaxis rugosa (RFC=0.019), Costus afer (RFC=0.019), Gymnanthemum amygdalinum (RFC=0.019), Jatropha curcas (RFC=0.019), Morinda lucida (RFC=0.025), Nauclea latifólia (RFC=0.019), Nicotiana tabacum (RFC=0.019), Saccharum officinarum (RFC=0.019), Anacardium occidentale (RFC=0.016), Annona stenophylla subsp.cuneata (RFC=0.016), Carica papaya (RFC=0.016), Dianthera secunda (0.016), Dorstenia psilurus (RFC=0.016), Gardenia ternifolia subsp. jovis-tonantis (RFC=0.016), Laportea aestuans (RFC=0.016), Mesosphaerum suaveolens (RFC=0.016), Millettia versicolor (RFC=0.016), Musanga cecropioides (RFC=0.016), Vitex madiensis (RFC=0.012), Aloe buettneri (RFC=0.012), Annona muricata (RFC=0.012), Aspilia kotschyi (RFC=0.016), Cymbopogon citratus (RFC=0.012), Aloe buettneri (0.012), Annona muricata (RFC=0.012), Aspilia kotschyi (RFC=0.012), Cymbopogon citratus (RFC=0.012), Psidium guajava (RFC=0.012), Sida acuta (RFC=0.012), Steganotaenia araliácea with RFC=0.012. Ethnomedicinal plant species with high RFC values indicate that they are widely used and known by local communities. The above shows that Persea amaerina was the most frequently cited plant for medicinal use, making it the plant species most widely used in local pharmacopoeia. (Masengo et al., 2024), in their study based on Inventory and ethnobotanical study of edible fruit plants in Uíge city, Northern Angola reported that the most commonly used medicinal plant species were Mangifera indica and Persea americana.