The multiregional study was carried out in three regions in Algeria: North-West, Kabylia (Center), and Sahara (South) (Figure 1). The ethnobotanical investigations in the North-West were performed in five departments: Mascara (area = 5,139 Km²), Oran (area = 2,114 Km²), Mostaganem (area = 2,269 Km²), Sid Bel Abbas (area = 9,150 Km²), and Tiaret (area = 20,673 Km²) and their surrounding villages located from the Mediterranean Sea to the Moroccan borders. Although no data is available regarding the flora of each department, that of the region of Oran showed the presence of 92 taxa; out of them, 72 remain endemic (Miara et al., 2018). The ethnobotanical study carried out in Center Algeria covered one city named Tizi Ouzou and its surrounding villages covering an area of 3,568 Km², located 100 km east of the capital (Algiers) and 30 km south of the Mediterranean Sea. Owing to its favorable climate, this region is characterized by an important vegetal diversity, including 659 species, 95 subspecies, 2 varieties, and 1 forma from 381 genera and 88 botanical families (Meddour and Sahar, 2021). The south areas included in the present study covered three of the main cities of the Algerian large desert: Ghardaïa (area = 32,256 Km²), Bechar (area = 161,400 Km²), and El Bayad (area = 71,686 Km²), characterized by important cultural, ecological, climatic, and botanical diversity (Taïbi et al., 2020; Taïbi et al., 2021). This desert wide region is characterized by sparse vegetation, grasses appearing during a short period of the year, and rare trees. According to its adaptation mode to the drought, Saharan flora can be divided into ephemeral plants, called “achebs” with a short vegetative cycle of one to four months, and perennial plants with morphological and anatomical adaptations based on an enhanced absorbent system and reduced evaporating surface. The local flora comprises 130 species belonging to 40 families (Chehma and Djebbar, 2008).

The ethnobotanical investigations were carried out from December 2019 to June 2020. During this period, we visited 13 cities and 19 villages in the study areas, searching for traditional healers. The data had been gathered from 40 informants; 87.5% of them were professionals, acquiring the therapeutic knowledge by the transition from generation to generation, and 12.5% were herbalists. The traditional healers were interviewed by a face-to-face interview in their homes or workplaces to fill out a questionnaire and collect the data. The responses included the demographic characteristics of healers (Table 1) and other information related to the uses of medicinal plants, such as the vernacular name, ailments treated, parts used, preparation, and administration modes. The species were given in their local names in Arabic or Amazigh.

The medicinal species mentioned by the traditional healers were collected, coded, and dried. Voucher specimens were deposited at the Herbarium of the Laboratory of Research on Biological Systems and Geomatics (LRSBG), University of Mascara, Algeria.

The taxonomic identification was performed by Professor Bachir Benarba using the standard literature (Baba Aissa, 1999; Kunkele and Lohmeyer, 2007; Trabut, 2015).

Table 2 shows more than 100 diseases recorded from the ethnobotanical investigations. All the ailments were classified into 17 categories based on the vital system/organ affected or type of damage.

Ethnobotanical indices, fidelity level (FL) and informant consensus factor (F_IC), were calculated to analyze the data obtained. Consensus indicators FL and F_IC were used to quantify the relevance and importance of a species for a given ailment category and the agreement of its use among healers, respectively (Hoffman and Gallaher, 2007; Khan et al., 2014). FL and F_IC were calculated using the following formulas (Morvin Yabesh et al., 2014):

Fidelity level: FL (%) = (Np/N)*100

Np is the number of use reports for a given species reported for a particular ailment category, and N is the total number of use reports cited for any given species.

Informant Consensus Factor: F_IC = (Nur-Nt)/(Nur-1)

Nur is the number of use citations in each category, and Nt is the number of species reported in each category.

This study revealed 167 species of medicinal species used for therapeutic purposes, belonging to 70 families. Lamiaceae (13%), Asteraceae (13%), Apiaceae (7%), Rosaceae (5%), and Fabaceae (5%) were the most cited families, while the 66 remaining families (57%) had between 1 and 5 species in each (Figure 2). As shown in Figure 3, the plant parts most frequently used were leaves (29%), followed by aerial part (23%), seeds (12%), fruits (9%), and flowers (7%). Some used parts were lower than those, such as roots (6%), bark (5%), and whole plant, bulb, wax, and stalk (2% each). Besides, peels, flower buds, stamen, and gum were slightly used (1%).

Regarding the preparation methods (Figure 4), decoction (35%), raw (24%), infusion (19%), paste (10%), and maceration (8%) were the dominant methods for remedies preparation. Surprisingly, the current study recorded burning (2%) as an uncommon/novel mode used by traditional healers. In addition, the common administration route was the oral ingestion (56%) followed by external application as an ointment on the skin and compress (27%), steam (11%), or internally tract as nasal inhalation (3%), intraear (2%), and the mouthwash (1%) (Figure 5). Of the remedy’s prescription, 64% of medicinal plants were mixed with other ingredients, and 36% were taken without addition. Indeed, there were 32 species combined with one plant, 21 plants with two plants, 19 plants with three or four plants, and 14 plants with more than four plants. Furthermore, some herbal mixtures (43%, n = 74 species) were prepared by adding different adjuvants (Figure 6). These adjuvants include honey (25 use reports) followed by olive oil (22), fat (8), vinegar (7), plant oil, and sulfur and tar (6 times each).

By comparing the data from this study with other ethnobotanical researches carried out in Algeria and neighboring countries (Morocco, Tunisia, Mauritania, Nigeria, and Mali), we found that 11% of total species have not been previously reported as medicinal plants. Of them, 11 species were documented in Sahara, 5 in Kabylia, and 3 in West Algeria. These species are used as remedies to treat both common ailments and incurable diseases. The new reports are listed in Table 3 with their vernacular names, parts used, therapeutic uses, and modes of administration.

Surprisingly, 4 out of the 19 new species (Lycium shawii Roem. and Schult, Humulus lupulus L., Crataegus azarolus L., Centaurea acaulis L., and Verbascum sinuatum L.) were highly cited by the informants. V. sinuatum is used to treat gastrointestinal and respiratory tract diseases such as pneumonia, using the decoction method with oral and topical application, respectively. The plant is termed locally “Moslih el-Andar” meaning in the local dialect “tract’s fixer” relating to its effect that repairs the continuous elongated anatomical structure in the body. Similarly, the decoction of L. shawii is used to treat two ailments categories: skin diseases (skin ulcers and leprosy) and skeletomuscular system disorder (osteoarthritis). Nevertheless, these ethnomedicinal uses and their pharmacological properties have not been documented in previous studies.

Furthermore, some species were previously reported to be used for culinary purposes such as Telephium imperati L. called in local dialect as tassarghit/sarghina. The stems of the plant are usually consumed as soup’ spice for postpartum women in Algeria (Sahara and Kabylia region). As reported here, for the first time, it is newly mentioned to be used for medicinal purposes by the local healers treating mouth ulcers and anemia. Moreover, we found that decoction of Quercus faginea Lam. seeds, a popular tree in West Algeria (Alcaraz, 1989), is used to treat sexual-reproductive problems besides the fruits (raw) of Lupinus micranthus Guss., a species widely distributed in Algeria and the Mediterranean countries (Msaddak et al., 2017). On the other hand, our results showed that species such as Phyllanthus niruri L., Hypecoum procumbens L., and Gentiana acaulis L. are used to treat skin diseases and cancer via topical application. These species have not been previously reported to be used as medicinal species in the Mediterranean region.

In the present study, we found that 89% of total species have already been mentioned as medicinal plants. In fact, more than 100 species cited in this survey were reported in previous studies from different regions of Algeria. Besides, we found that, despite having similar therapeutic uses, the species had different vernacular names from a region to another. Interestingly, we report here 47 new therapeutic uses for 20 known plant species. Table 4 shows these new uses compared to those previously reported in the world.

Table 5 shows the 16 ailments categories arranged in descending order based on the F_IC values. Cancer had the highest F_IC value of 0.49 with 44 species used, such as C. colocynthis, Panax ginseng C.A. Mey., E. alata, Aquilaria malaccensis, Aristolochia longa L., and Taraxacum officinale. On the other hand, we found that sexual-reproductive problems (F_IC = 0.46), gastrointestinal system diseases (F_IC = 0.44), and skeletomuscular system disorders (F_IC = 0.39) were recorded to have the second, third, and fourth highest F_IC values, respectively. Respiratory tract diseases were ranked to be the fifth ailment group with an F_IC value of 0.36.

According to their knowledge and experience, the local healers preferred some species to treat particular diseases. The highest FL values of the commonly used plants are listed in Table 6. Our results indicated that M. vulgare, A. herba-alba, Z. officinale, and J. phoenicia had the absolute FL value of 100% in several ailment categories (SRD, cancer, respiratory diseases, and GISD).

In the present study, we recorded 167 species belonging to 70 families with a dominance of Lamiaceae, Asteraceae, Apiaceae, Rosaceae, and Fabaceae. Our findings agreed with those we previously reported. Indeed, in Mascara (North-West Algeria), most of the medicinal species used by local healers belonged to these five families (Benarba, 2015). Similar findings were reported in Algeria (Miara et al., 2018; Taibi et al., 2020), Morocco (Barkaoui et al., 2017; Skalli et al., 2019), and Italy (Tuttolomondo et al., 2014). It has been suggested that plants belonging to these families are mainly used by local populations in Africa owing to their pharmacological effects offering a cheap therapeutic alternative (Sawadogo et al., 2012). Furthermore, leaves, aerial parts, and seeds were the most frequently used parts by local healers. Our results confirm the dominance of leaves as the most common used important plants’ part used in local phytotherapy as has been demonstrated in Algeria (Benarba, 2015; Benarba, 2016; Bouasla and Bouasla 2017; Miara et al., 2018; Taibi et al., 2020) and neighboring countries such as Mauritania (Yebouk et al., 2020), Morocco (Barkaoui et al., 2017; Skalli et al., 2019), or Italy (Leto et al., 2013). The dominance of leaves in most of the ethnobotanical studies could be explained by their ease collecting and abundance besides the fact that they are considered the site of photosynthesis and therefore of bioactive molecules.

Our results showed that the traditional healers used different preparation methods, including decoction, infusion, paste, or maceration. Decoction was found to be the preferred method. Similar results were found in previous ethnobotanical studies (Benarba, 2015; Merrouni and Elachouri, 2020). In fact, decoction and infusion were found to be the most used in the recent ethnobotanical studies in Algeria (Benarba et al., 2015; Benarba, 2016; Mechaala et al., 2021; Zatout et al., 2021) and neighboring countries such as Tunisia, Egypt, Spain, and Italy in Africa and in Europe (Giday et al., 2009; Benitez et al., 2010; Amri and Kisangau, 2012; Menale et al., 2016; Savić et al., 2019). The dominance of decoction or infusion could be explained by the disinfection potential of heating besides its extraction enhancing effects (Benarba, 2015).

We also found that oral ingestion was the most frequently used mode of administration, followed by external application, steam, and nasal inhalation. Our findings are consistent with those we previously reported in South-West Algeria (Benarba, 2016), North-West Algeria (Benarba, 2015), and Extreme-West Algeria (Tlemcen) (Zatout et al., 2021). Likewise, oral and topical applications were found to be the most frequently used administration methods used by local healers or populations in other regions in Algeria (Hammiche and Maiza, 2006; Boudjelal et al., 2013; Sarri et al., 2014; Miara et al., 2018) and neighboring countries (Mrabti et al., 2019; Fakchich and Elachouri, 2014; Benitez et al., 2010). In this same line, oral and topical administrations are frequently used in traditional medicine. The choice of administration routes is based on the pharmacological effect of each species, the therapy target, duration, and the limitation of treatment to a precise area (Sargin et al., 2015; Benarba, 2016).

The traditional healers in the study areas reported that 64% of medicinal species were mixed with other medicinal plants, whereas 43% of herbal mixtures were prepared by adding different adjuvants with a dominance of honey, olive oil, animal fat, or vinegar. In concordance with our findings, several ethnobotanical investigations carried out in Algeria demonstrated that honey was the adjuvant most frequently added to prepare medicinal herbal mixtures (Benarba, 2016; Ouelbani et al., 2016; Zatout et al., 2021). Our findings are also in perfect consistency with those reported in other regions around the world (Yabesh et al., 2014; Amri and Kisangau, 2012; Pranskuniene et al., 2016). These ingredients could enhance the plant effect, maintain the blend texture, and facilitate the treatment administration. To the best of our knowledge, some adjuvants were not previously mentioned, such as tar and litharge.

In the present study, 11% of the recorded 167 species have not been previously reported as medicinal plants in Algeria and neighboring countries in the Mediterranean basin. Moreover, more than 100 species reported here were previously reported to be used for therapeutic purposes in North-West (Benarba, 2015), South-West (Benarba, 2016), and North-East Algeria (Boual et al., 2020). Although each species had mostly the same therapeutic uses, for example, A. herba-alba, Punica granatum L., and Senna alexandrina Mill. were used mainly to treat gastrointestinal disorders, their vernacular names differed from one region to another such as Aquilaria malaccensis Lam. called Oud El-Rih in the West and A-ghriss in Sahara. These findings are in agreement with those reported in Algeria (Benarba, 2015; Bouasla and Bouasla, 2017 ), Morocco (Chaachouay et al., 2020; Merrouni and Elachouri, 2020; Yebouk et al., 2020), and other countries such as Yamen, Turkey, India, and China (Prabhu et al., 2014; Polat, 2019).

Interestingly, our findings report 47 new therapeutic uses for 20 known plant species. In the present study, we found that local populations living in the study areas used Carlina gummifera (L.) Less. to treat infertility, uterine problems, urinary tract infection, bladder disease, and osteoarthritis, whereas the plant uses previously reported included epilepsy, psoriasis, ulcers, and hemorrhage (Ahid et al., 2012; Hammiche et al., 2013). Likewise, leaves of Cymbopogon schoenanthus (L.) Spreng. were found to be used in the treatment of several types of cancer in the study areas. This use is reported for the first time since the plant was previously reported to be used mainly to treat termites and bruchid (Koba et al., 2007). Prunus persica, usually used against cough, constipation, and menstruation absent (Lin et al., 2021; Al-Fatimi., 2019), was reported by local populations to treat skin diseases.

Regarding the informant consensus factor, the highest F_IC value was recorded for cancer (F_IC = 0.49) with 44 medicinal species used. This is the first study carried out in the three regions (West, Sahara, and Kabylia) of Algeria at the same time, calculating the informant consensus factor (F_IC). Our results revealed that cancer seems to be one of the most prevalent diseases in the study areas since no previous investigations had found cancer as the first ailment category according to their F_IC values. In fact, cancer has become a public health issue due to an increasing incidence, with 19.3 million new cases and about 10.0 million deaths worldwide in 2020 (Ferlay et al., 2021). Likewise, cancer incidence is increasing in Algeria. Actually, Algeria has the highest incidence of gastric (6%) (Behar et al., 2021) and liver cancer (Benarba and Meddah, 2014) when compared to North African countries. Moreover, breast and thyroid cancer incidence rose significantly in the last two decades (Mehemmai et al., 2020; Halfaoui et al., 2021). This pattern may be attributed to several causes, such as a westernized lifestyle, contaminated foods, pollution, and deteriorated living conditions. Furthermore, sexual-reproductive problems, gastrointestinal system diseases, skeletomuscular system disorders, and respiratory tract diseases were recorded to have higher F_IC values. In a previous study carried out in North-West Algeria, we found that gastrointestinal diseases had the highest F_IC value of 0.658, followed by general health (F_IC = 0.645) and respiratory diseases (0.642), while the cancer category was recorded to be the 4th highest (F_IC = 0.524) (Benarba et al., 2015). Moreover, a recent study carried out in the extreme North-West of Algeria reported that the reproductive and sexual disorders F_IC value were the highest score (0.98), and for the cancer category, they had an F_IC value of 0.77 with 6 species (Zatout et al., 2021). In disagreement with our findings, Bouasla and Bouasla (2017) indicated that cancer (F_IC = 0.25) was the least known ailment to be treated in the traditional medicine of the local population in North-East Algeria.

According to our results, M. vulgare, A. herba-alba, Z. officinale, and J. phoenicia had the absolute FL value of 100% in several ailment categories (SRD, cancer, respiratory diseases, and GISD). These findings are in agreement with those previously reported in different neighboring regions (Benarba et al., 2015; Bouasla and Bouasla, 2017; Chaachouay et al., 2020). Besides these species, Parietaria officinalis L. was found to possess an FL of 100% for kidney diseases which is consistent with findings previously reported in North-West Algeria (Benarba, 2016) and Morocco (Ammor et al., 2020). Inconsistent with our previous findings in both North-West (Benarba et al., 2015) and South-West Algeria (Benarba, 2016), T. vulgaris was the only species having the highest FL of 100% for skin diseases. This could be attributed to its antifungal and antimicrobial potentials demonstrated against the main pathogens causing skin diseases (Tadele et al., 2009; Vinciguerra et al., 2019). Recently, a facial phytocosmetic preparation from T. vulgaris was found to possess promising antiskin aging effects, as shown by enhanced adipogenesis through upregulation of PPAR-γ expression (Caverzan et al., 2021).