The main study was conducted at the University of Fort Hare, Alice Campus (–32°46’59.99” S 26°52’59.99” E), situated at an elevation of 524 m above sea level within the Raymond Mhlaba Municipality, Amathole District, Eastern Cape, South Africa. Questionnaires were administered across three study sites: Zidindi village (31°58’60” S; 29°1’0” E) in the King Sabatha Dalindyebo Municipality, and the townships of Motherwell (33°48′14″S 25°34′48″E) in the Nelson Mandela Bay Metropolitan Municipality (NMBMM) and Mdantsane (32°57’0”S; 27°46’0”E) in the Buffalo City Metropolitan Municipalities (BCMM) (study sites 1–3; Figure 1). According to informal census estimates, study site 1 (Zidindi) is a small rural settlement near the Wild Coast Coffee Bay, with a population of less than 100 residents. The area experiences a wet climate with an annual average rainfall of 1059 mm. Study site 2 (Motherwell) receives an annual average rainfall of 529 mm, while study site 3 (Mdantsane) has an average annual rainfall of around 850 mm.

Ethnobotanists have traditionally relied on the collection of voucher specimens and their deposition in herbaria for accurate plant identification (Greene, Teixidor-Toneu & Odonne 2023). According to Dold and Cocks (2002), the use of vernacular names to identify medicinal plant species in informal markets is unreliable, as these names often vary across regions and even among traders within the same market. To address this challenge, volunteer respondents assisted in identifying plants by their vernacular names at each study site, after which voucher specimens were collected and deposited in the Department of Botany Herbarium, University of Fort Hare (Alice Campus), for authentication.

Both traditional healers and street vendors were informed that the surveys were undertaken exclusively for research purposes, and that the information provided would contribute to the protection and preservation of traditional knowledge of indigenous plants, the enhancement of rural health and livelihoods, and the potential discovery and development of novel herbal medicines aimed at addressing the socio-economic challenges of their communities and South Africa more broadly. Before participation, all respondents were required to sign the University of Fort Hare informed consent form.

This study focused on evaluating and assessing the underutilised coastal indigenous plants with therapeutic effects in the Eastern Cape. A well-structured set of questionnaires with open- and closed-ended questions were allocated to 35 respondents, including nine street vendors in Motherwell, five traditional healers and five street vendors in Mdantsane, as well as four traditional healers and 12 street vendors in Zidindi, before the study. The sample size (N = 35) may appear relatively low compared to the wider population of the study sites; however, the study specifically focused on indigenous coastal flora and therefore purposively targeted respondents who specialise in these species or possess significant knowledge. Similar ethnobotanical surveys have used comparable sample sizes, for example, Rasethe, Semenya and Maroyi (2019) identified medicinal plants traded in informal herbal markets across five districts in the Limpopo Province using 35 respondents. Empirical syntheses show that theme saturation is often achieved with approximately 9–17 interviews in homogenous participant groups, while meaning saturation may require about 24 interviews, and theoretical saturation can be reached within 20–30 or more interviews, depending on study complexity (Green and Thorogood 2018; Wutich, Beresford & Bernard 2024). Furthermore, the concept of information power emphasises that sample adequacy is determined by the specificity and richness of data, thereby supporting the sufficiency of 35 expert respondents in generating robust and reliable findings (Malterud, Siersma & Guassora 2016).

The discussions were held in isiXhosa, isiZulu and English, respectively, because 30 out of the 35 street vendors were of Xhosa descent and the remaining five were of Zulu descent. The main questions included: (1) the number of years of experience in growing and/or selling these plants; (2) their medicinal uses; (3) their preparation and administration methods and (4) their effectiveness. The effectiveness in this study refers to the perceived success or reliability as reported by the respondents, rather than clinically tested efficacy. Followed by validation through respondent consensus, wherein two or more participants provided similar or identical responses, regardless of the method of administration (Afolayan et al. 2014).

Ethical clearance to conduct this study was obtained from the University of Fort Hare Inter-Faculty Human Research Ethics Committee. The ethical clearance number is WIT031SSOG01.

The demographics of the respondents are recorded using Table 1. The ages of the respondents were between 30–63-years-old, and 25.7% (n = 9) of them were 30–39-years-old, 20% (n = 7) were between 40-49-years-old, 37.1% (n = 13) were 50–59, and finally 17.1% (n = 6) were 60-63-years-old. More than half the respondents, 51.4% (n = 18), were female and 48.6% (n = 17) were male. About 25.7% of them were traditional healers from Mdantsane and Zidindi, and 74.3% were street vendors from all three study areas. Their educational background ranged from none to secondary school, where 8.5% (n = 3) of them were illiterate, 40% (n = 14) attended primary school, and more than half of the respondents, 51.4% (n = 18), had a high school education. Their experiences working with indigenous plants ranged from 5–35 years, and more than half of them, 25.7% and 28.6% had been working with these plants for more than 20 years, while the newcomers, 14.3% (n = 5), had been in the business for 5–10 years.

The ages and the experiences of the respondents were observed to be correlated to each other; those within the age bracket of 50–63-years-old were found to have more experience and insights than the younger generation, regardless of their educational background. They revealed that they obtained most of their indigenous knowledge through word of mouth from their parents and forefathers. The majority of the youngest group (30–39-years-old) acquired their ethnomedicinal knowledge through spiritual callings, as they are traditional healers, while the remaining few street vendors gained theirs through informal apprenticeship, primarily by observation and practice.

These findings correspond with a survey conducted by Falemara et al. (2021) whereby it was found that the older generation had more traditional knowledge of the indigenous plants surveyed than the youth. This observation may vary across different areas because of variability in socio-economic development. For instance, a survey conducted by Olanipekun et al. (2016) showed that the younger people contributed a significant traditional knowledge of indigenous plants compared to elders.

Furthermore, the demographic profile of the study shows that more than half of the respondents (51.4%) were female, which suggests that women are more hands-on when it comes to the knowledge and production of medicinal plants than men in the study sites. In accordance with the study conducted by Sumardjo (2021), it was reported that the majority of the respondents were women and they possessed and shared a deeper understanding of indigenous medicinal plants.

Data were analysed using Statistical Package for the Social Sciences (SPSS), as well as use-value and fidelity level metrics. Use-value was calculated using Equation 1, as simplified by Albuquerque et al. (2006): UV=∑UiN[Eqn 1] where ΣUi is the sum of all the plant uses cited by the respondents

N is the total number of all the respondents interviewed

Fidelity level was used to measure the importance and popularity of the plant for a particular disease and ailment from the respondent, and it was calculated using Equation 2 as described by Friedman et al. (1986): FL=NpN×100[Eqn 2] where Np denotes the number of respondents who cited the plant for a specific disease/ailment.

N denotes the total number of respondents who cited the plant for any disease/ailment.

A total of 21 unique families encompassing 24 species of coastal indigenous plants were selected and recorded for this study using a purposive selection, focusing on underutilised, coastal indigenous medicinal plants used by selected local communities in the Eastern Cape. The scientific names and authorities were verified using the World Flora Online (WFO; https://www.worldfloraonline.org) and the African Plant Database (AFD; https://africanplantdatabase.ch).

The most represented family was Asteraceae, comprising four plants (Tarchonanthus camphoratus, Helichrysum cymosum, Gazania rigens and Eriocephalus africanus) (Table 2) and all of them are used as an analgesic to relieve pain in wounds, cuts, headache, earache, etc., except for E. africanus, which is used as an anti-inflammatory for arthritis. Aizoaceae was the second most represented family with three plants (Carpobrotus edulis, Tetragonia decumbens and Aptenia cordifolia). Each species recorded was found to cure more than one ailment; for instance, A. cordifolia was found to treat nine diseases and ailments with a 77.8% fidelity level. The majority of these plants have multiple pharmacological effects against major human diseases such as cancer, tuberculosis and diabetes, which are some of the leading causes of death.

According to Table 3, the use-values and fidelity levels of these plants are significantly high, suggesting a higher accuracy and effectiveness, implying that they can be safely used as herbs and pharmaceuticals to treat various diseases and ailments cited in this study. Furthermore, the World Health Organization (WHO) states that ‘herbal remedies fulfil the health requirements of around 80% of global populations, particularly for millions residing in the extensive rural regions of developing nations’ (Hosseinzadeh et al. 2015).

Descriptive analysis of the commonly used plant parts in the preparation of herbal medicine was performed using SPSS, with data derived from Table 3. As seen in Table 4, leaves were used 87.5% of the time to treat one or more of the reported diseases and ailments, with roots being the second highest part used (70.8%), followed by bark (33.3%), flowers (25%) and fruit and stem both (20.8%), and the whole plants (8.3%) were the least used in the preparation of herbal medicine.

Leaves and roots were reported to be the most frequently used parts in the preparation of herbal medicine to treat one or more of the cited diseases and ailments in this study, which is similar to the survey conducted by Hughes et al. (2015) and Sumardjo (2021), who observed that leaves were the most used parts in their study. According to Semenya, Potgieter and Tshisikhawe (2013), the notable use of these plant parts is attributed to the longstanding belief that they have greater healing contents than other parts. Furthermore, the leaf surface of a plant makes up the primary photosynthetic region and the most biochemically active part, and this boosts the formation of secondary metabolites, which contribute to its therapeutic properties (Ghorbani 2005). While plant roots, with their stable environment and low metabolic activity, store secondary metabolites with minimal fluctuation, leading to higher concentrations of bioactive compounds.

Medicinal plants can be prepared in various methods for diverse applications. This study documented six preparation modes (Table 5), such as decoction (66.7%), boiling (25%), burning (29.2%), infusions (54.2%), poultice (20.8%) and raw consumption (8.3%). Decoction was identified to be the most commonly used mode of preparation, which can be easily achieved by boiling water with the specific plant part until the water volume is reduced to half of its initial volume to effectively extract the bioactive compounds and micronutrients. This observation is consistent with numerous previous studies, including the results of the study conducted by Amel et al. (2013) and Youbi et al. (2016). The widespread use of decoction is attributed to its effectiveness and easy preparation.

Herbal medicine is predominantly administered gastro-internally and/or dermally. Oral ingestion (87.5%) was the most prevalent administration method used in this survey (Table 6), with decoction and infusions the frequently utilised preparation methods. Erhabor, Idu and Udo (2013) and Kadir et al. (2014) reported the same observation in a similar survey in Nigeria and Bangladesh, respectively. Eleven plants were reported to be administered topically (45.8%), while 12.5% were consumed raw, either by chewing and/or chewing and spitting the leaves or roots; however, they are recorded with the same percentage in this study. Nasal inhalation was 25.0% of the time to administer herbal medicine in this study.

In this survey, it was reported that ailments such as gastrointestinal issues, headache, flu and cold were treated by oral ingestion of E. africanus, Oxalis pes-caprae, Salvia lutea, Helichrysum cynosum, Carissa macrocarpa and C. edulis prepared by boiling, decoction or infusion. On the other hand, external issues, such as snake and tick bites, bone fractures, wounds, sores, rash, eczema and acne were treated by rinsing or smearing the affected area with a burnt and crushed Ziziphus mucronata, Harpephylum caffrum, C. edulis powder. Each plant was reported to cure more than one disease/ailment, while different plants were also found to share common therapeutic applications, with varying fidelity levels. However, several studies have reported the toxicity of herbal and traditional medicines. Bose et al. (2021) attributed this toxicity to misidentification and authentication, incorrect standardisation or labelling, and contamination with fungal toxins such as aflatoxins. To address these risks, the World Health Organization recommends a series of toxicity assessments, including acute, chronic, local and specialised testing (Bose et al., 2021).

Numerous studies in the previous years have reported herbs as the most common medicinal life forms. Few studies, including the recent surveys conducted by Falemara et al. (2021), reported trees as the most commonly used plant life form in the production of therapeutic remedies. This survey recorded shrubs (41.6%) as the prevalent life form used in the preparation of herbal medicine by the selected local communities in this study, followed by trees (37.5%), herbs (16.7%) and groundcover (12.5%) (see Figure 2). These findings are validated by the study carried out by Maroyi (2013), who documented trees and shrubs as equally predominant used life forms in the preparation of herbal medicine in Zimbabwe.

The frequent utilisation of shrubs over other life forms is attributed to their availability throughout the year because they are fairly drought-resistant and not affected by seasonal changes (Maroyi 2013). Shrubs have more foliage and aerial parts compared to herbs and groundcovers; therefore, the locals harvest sustainably without severely depleting the aerial parts, which might interfere with the physiological functions, which in turn impacts the plants’ ability to regenerate (Tugume et al. 2016).

Furthermore, shrubs play a vital role in ecosystem stability by preventing soil erosion, especially in the Eastern Cape, where degraded arable land is prevalent. Moreover, shrubs possess more secondary metabolites because of a larger surface than groundcovers or small herbs.

The South African National Biodiversity Institute (SANBI) recognises the International Union for Conservation of Nature (IUCN) Red List as the global benchmark for assessing species’ risk of extinction, and this framework is used in compiling the national Red List of South African plants (Fajinmi et al. 2023). The Red List provides an evidence-based assessment of extinction risk, highlighting species most urgently in need of conservation and protection. However, while its approach effectively prioritises threatened species, it does not emphasise those considered at low risk/least concerned. For example, according to SANBI records, 100% of the plants recorded in this study are classified as least concerned (LC) or under-utilised, yet species such as Dasispermum suffruticosum remain rare to find in their ecological habitats despite their LC. This is attributed to the combination of biological, ecological and anthropogenic factors, such as poor seed germination rate, competition with invasive species and habitat loss and degradation by human activities, respectively. Therefore, stricter regulatory measures need to be implemented to protect and conserve these species to ensure their continued availability for future generations and to support ongoing research and development related to their ethnobotanical and ethnomedicinal uses. Another two plant species that are not entirely underutilised in the Eastern Cape, as indicated by IUCN, are H. cymosum and T. camphoratus (camphor bush). These two plants form the backbone of traditional herbal medicine in the majority of rural communities, addressing a wide range of conditions, from minor ailments requiring analgesic relief to pulmonary conditions requiring antitussive action. Their efficacy has been validated by numerous studies. Fajinmi et al. (2023) also found that some of the highly and frequently utilised medicinal species may still be classified as ‘Least Concern’ because of their broad range of distribution, leading to overharvesting and affecting their conservation status.

Globally, the demand for plant-derived products continues to rise, with the market for medicinal plants expected to reach approximately USD 450 billion (ZAR 7.98 trillion) by 2025 (WHO 2023). Historically, a number of blockbuster drugs have originated from plants, including morphine from Papaver somniferum, aspirin from Salix cortex and digoxin from Digitalis purpurea (Nath et al. 2023), while in South Africa, species such as Siphonochilus aethiopicus (African ginger), Aspalathus linearis (rooibos), Hoodia gordonii (Bushman’s hat) and Agathosma betulina (buchu) have successfully entered global markets.

In 1998, approximately 20 000 tons of plant materials were traded, valued at around USD 38 million (Rasethe et al. 2019). In 2011, the South African bioprocessing sector, which includes both primary and secondary processing of indigenous plant resources, was valued at ZAR 482 m, reflecting its growing contribution to national economic development (South African Department of Forestry, Fisheries and Environment n.d.). Beyond direct trade, the commercialisation of medicinal plants also supports the pharmaceutical, nutraceutical and cosmetic industries. This creates opportunities for job creation, innovation and bioprospecting investments, which contribute to both rural and national economies. For example, Meke et al. (2017) reported that over 90% of medicinal plant traders in central and southern Malawi earned more than 50% of their households’ income through herbal medicine sales. However, the trade of these plants presents several challenges. Unsustainable harvesting has led to critical declines in some species; for instance, Siphonochilus aethiopicus is now classified as highly endangered in South Africa, largely extinct in the wild, and extremely rare because of extensive commercial exploitation in informal markets such as ‘muthi’ shops (Seile et al. 2022). Therefore, to prevent similar declines among the coastal flora recorded in this study, the cultivation of these plants, coupled with proper legislation and management strategies, is strongly encouraged.