2.1. Study Area

This research was conducted in the eastern region of Indonesia, precisely in Gorontalo Province which consists of five regencies and one city, with a total population of 1,180,948 people. The area with the most populous population is Gorontalo Regency followed by other areas, namely Bone Bolango Regency, Pohuwato Regency, Boalemo Regency and North Gorontalo Regency. Gorontalo Province is located in the northern part of Sulawesi Island, precisely at 0° 19′ 00″ to 1° 57′ 00″ north latitude and 121° 23′ 00″ to 125° 14′ 00″ east longitude of the Greenwich meridian. The location of Gorontalo Province is very strategic because it is flanked by two waters, namely Tomini Bay to the south and Sulawesi Sea to the north. The total area of Gorontalo Province is 12,435.00 km², with most of the land surface being hills and having many mountains with different heights. The forest area of Gorontalo Province is 764,881.23 ha and generally consists of 25.69% conservation forest; 26.45% protected forest; 11.78% fixed production forest; 33.03% limited production forest; and conversion forest amounting to 3.04% of the total forest area of Gorontalo Province. In addition, the geographical location and elevation can be seen in Figure 1. There are 35 villages were the lowest is 3 meters above sea levels (North Buntulia Village) and the highest 692 meters above sea levels (Persatuan Village).

2.2. Field Interview Methods

The ethnomedicinal survey was carried out from June 2021 to March 2022. The number of samples in this study was 105 people, referring to the literature which states that for ethnographic research, including ethnomedicine, the number of respondents interviewed was 30–60 people, which was considered representative enough or reached a saturation point, where no new data were obtained [15, 16]. Ethnomedicinal data collection was carried out using field surveys, open interviews and semistructured questionnaires. Ethnobotanical information was collected through a questionnaire that had previously been tested in the existing format (the ethnobotanical survey pro forma was designed and pretested with local informants, then modified based on the informants’ feedback), direct observation, discussions and interview methods [17]. The questionnaire was designed to capture information including plants used for the treatment of cough, colds, fever, dizziness and diarrhoea—several diseases related to mild COVID-19 symptoms; local name, part of the plant used, method of preparation and administration and side effects after taking the herbal ingredient. Informant biodata including age, gender, place of residence, educational and occupational background were also recorded. The informants were selected purposively using the snowball technique, where key informants (one per regency) who then recruited by other competent informants (20 per key informant) into the survey [18]. Key informants are considered to be important members of community who were observant, reflective, knew much about the culture, as well as able and willing to share their knowledge. Moreover, all informants are people who live in the study area, are over 18 years old and have been using medicinal plants to treat several diseases related to mild COVID-19 symptoms for at least the last three to five years. All informants were informed of the research concept to ask for their consent and willingness to participate in the survey. Informants who are willing to be asked individually about their knowledge regarding the use of plant species to treat several diseases related to mild COVID-19 symptoms, in this case cough, colds, fever, dizziness and diarrhoea.

2.3. Plant Collection and Identification

Plant species taken directly from informants were initially identified using local names and then identified by respective scientific classifications through relevant literature [19, 20]. Voucher specimens are prepared, identified and stored at the Department of Pharmacy, Faculty of Sport and Health, Universitas Negeri Gorontalo, Gorontalo, Indonesia.

2.4. Ethnomedicinal Data Analysis

3.1. The Demographic Characteristics of the Informants

A total of 105 local informants (28 males and 77 females) aged between 21 and 80 years were interviewed from 35 villages (see Figure 2). Demographic characteristics including gender, age group, education level and occupation are recorded (see Table 1).

3.2. Botanical Diversity

In the current study, 82 locally used species of medicinal plants from 40 families were recorded for the treatment and management of several diseases related to mild COVID-19 symptoms such as cough, colds, fever, dizziness and diarrhoea in the study area (see Table 2). Zingiberaceae, Euphorbiaceae and Lamiaceae are the three main families most representative for the 82 species documented as remedies against cough, colds, fever, dizziness and diarrhoea. Zingiberaceae have eight species, while Euphorbiaceae and Lamiaceae each have seven species (see Figure 3) and the other 37 families each have one representative species.

Information on local names, drug use, plant parts used, preparation and administration methods is also shown in Table 2. Based on UR data, the most widely used species to overcome cough are Plectranthus scutellarioides (41 UR), followed by Zingiber officinale (24 UR), Curcuma longa (19 UR) and Citrus aurantiifolia (10 UR). Another ethnomedicine study revealed that P. scutellarioides was used as a potent cough medicine by traditional medicine in the eastern highlands’ region of Papua New Guinea [25]. In vitro studies revealed that P. scutellarioides leaf extract was shown to have antibacterial activity against test bacteria that cause cough such as Streptococcus pneumonia, Klebsiella pneumonia, Staphylococcus aureus, Staphylococcus epidermidis, Enterobacter agglomerans and Candida albicans fungi, with a minimum inhibitory concentration (MIC) of 0.1%–0.75% w/v, and a minimum killing concentration (MKC) of 0.25%–1.75% w/v [26]. The extract also has the potential as a sputum diluent based on a decrease in mucus viscosity with a concentration of 0.01%–0.1% w/v. The effective dose of P. scutellarioides leaf extract that can be used as a reference to cure sputum is 1.75% w/v which is equivalent to seven fresh P. scutellarioides leaves [26].

To overcome colds, Z. officinale (19 UR) are most widely used, followed by Ocimum basilicum (17 UR). In silico studies with molecular docking revealed that the active compound allicin present in Z. officinale has anti-influenza cytokines [27]. In vitro studies revealed that crude extract mixtures of Z. officinale, honey and garlic inhibited influenza A virus growth in human peripheral blood mononuclear cells cultured [28]. Z. officinale ethanol extract has also been reported to inhibit the growth and development of H5N1 virus in a dose-dependent manner [29]. In vivo studies have revealed that treatment with gingerenone A, a compound isolated from Z. officinale, can suppress the replication of influenza A virus in the lungs of H5N1 virus-infected mice, reduce body weight loss and prolong their survival [30].

To overcome fever, a widely used species is Bryophyllum pinnatum (15 UR), followed by C. longa (15 UR), Jatropha curcas (14 UR) and Z. officinale (12 UR). B. pinnatum leaf methanol extract has been studied for anti-inflammatory, analgesic and antipyretic activity in animal models. The extract resulted in significant inhibition of carrageenan-induced paw oedema, significant reduction in cotton pellet granuloma in rats, inhibition of acetic acid-induced writhing in rats and significant dose-dependent reduction of yeast-induced fever [31]. Allium sativum (17 UR) and Z. officinale (10 UR) are widely used to deal with dizziness. A case study report in Australia revealed that administration of 1.2 g aged garlic extract (AGE) as a daily food supplement intervention was able to reduce the frequency and severity of headaches experienced by patients with suboptimal management of episodic tension headache after 6 weeks of treatment [32]. The effect is thought to be derived from the powerful anti-inflammatory effect of AGE on microvasculature [33]. AGE, a stable homogeneous extract rich in S-allyl-cysteine, may increase microvascular dilatation as a consequence of increased or imitation of prostaglandin vasodilatation [34].

Meanwhile, Psidium guajava (69 UR), both leaves and fruits, became the most widely used species to overcome diarrhoea, followed by Myristica fragrans (20 UR) and C. longa (13 UR). In vitro studies revealed that P. guajava has antibacterial activity against diarrhoea-causing bacteria such as Escherichia coli, Salmonella sp., Shigella sp., Staphylococcus aureus and Vibrio cholerae [35–37], and antivirals against rotaviruses causing diarrhoea in simians [38]. Spasmolytic activity of P. guajava against ileum isolated from guinea pig has also been reported [39–41]. The administration of P. guajava leaf extract in various animal models of diarrhoea such as mice [42, 43], rats [44–46] and rabbits [47] showed significant antidiarrheal activity. Quercetin as the main biomarker in P. guajava contributes to antidiarrheal activity through the mechanism of inhibition of intestinal secretion, reduction of nitrate oxide production and inflammatory expression and reactivation of Na⁺/K⁺-ATPase activity [48], as well as inhibition of SepA protease activity, a protein produced by S. flexneri [49]. Clinical studies revealed that the administration of P. guajava in 62 patients with rotavirus enteritis had a good curative effect with a recovery rate of 87.1% and a shorter diarrhoea discontinuation time (25.1 ± 9.5 h) compared to the control [50]. In addition, a randomised, double-blind clinical study of 50 patients with acute diarrhoea who received the product P. guajava leaf capsule (500 mg) orally every 8 h for 3 days reported that the product could reduce the duration of abdominal pain in patients [51]. In addition, we have summarised the reported bioactivities and isolated compounds or extracts that are relevant to the use of plant species with high reported use for treating coughs, colds, fever, dizziness and diarrhoea (see Table 3).

3.3. Ranking of the Most Important Medicines

Although the number of plant species used for the treatment and care of several diseases related to mild COVID-19 symptoms is relatively high, their ethnobotanical indices include RFC (0.01–0.41) and FL (1%–41%) generally low (see Table 2). Furthermore, several diseases related to mild COVID-19 symptoms (where the informants offered treatment and declared themselves cured) were divided into five disease categories, and the informants’ level of agreement with their treatment was evaluated. The categories of diarrhoea (ICF 0.85), cough (ICF 0.78), colds (ICF 0.73), dizziness (0.72) and fever (ICF 0.71) showed relatively stronger agreement between the informants (see Table 4).

The results show that diarrhoea has the highest ICF value, which indicates that the plant is widely known and often used in society for certain health problems. In addition, there is significant cultural importance associated with the use of this plant, which encourages collective understanding of its benefits. These findings correlate with other studies reported by Bhagawan et al. [68] among the Tengger Tribe Community who live in Argosari Village, East Java, Indonesia. A high ICF value reflects the popularity and effectiveness of this plant-based medicine among the informants. This shows that the local community really appreciates the medicinal properties and various uses of this plant.

However, current research reveals that P. guajava is the most popular plant species with a high index value (RFC 0.62, FL 62%), which can be taken as a signal of the excellent curative potential of the plant. Khan et al. [69] revealed that plants used repeatedly were more phytochemically active. Quercetin, which is the most dominant flavonoid in P. guajava, shows strong antidiarrheal activity [70]. The antidiarrheal activity of quercetin is thought to be derived from the relaxing effect on the intestinal muscle layer that prevents intestinal contraction [71].

3.4. Plant Parts Used

Diverse plant parts such as leaves, rhizome, fruit, bulb, shoot, flower, stem, seed, bark, epicarp and latex are used to overcome several diseases related to mild COVID-19 symptoms that have been reported by informants (see Figure 4). However, leaves (46.46%) were the main plant used to overcome several diseases related to mild COVID-19 symptoms, followed by rhizome (23.53%) and fruit (11.92%).

These results show the widespread use of leaves as the main part of plants in the manufacture of traditional medicines to treat human health problems. In particular, this study determined that leaves are the part of the plant most widely used to treat human diseases in the region, a finding that is consistent with various other studies conducted in various regions in Indonesia [72]. There are several reasons that can explain the dominance of leaves in traditional drug formulations for human health. As pointed out by Bekele et al. [73], leaves are often preferred because of their relative ease of preparation and the potential therapeutic benefits they offer compared to other plant parts. Leaves are generally easier to obtain, easier to harvest and may contain higher concentrations of active medicinal compounds, making them a practical choice for the manufacture of traditional medicines. Overall, these insights can inform the development of sustainable harvesting practices and conservation strategies to ensure the continued availability of this valuable natural resource.

3.5. Preparation and Application Modes

To prepare medicinal plants to overcome several diseases related to mild COVID-19 symptoms, the informants identified 12 methods in which most (about 31.70%) were prepared by boiling (see Figure 5). These results show consistency with the findings of previous studies [74], which was carried out in the western region of Indonesia, namely Java and Bali. According to Kamatenesi et al. [75], boiling helps extract active ingredients from parts of medicinal plants which can increase the efficacy of medicines against various diseases, as well as preserving herbal medicines longer than using cold extraction. However, in some cases, boiling can cause degradation of bioactive materials, especially aromatic compounds, if it takes a long time [76]. This highlights the importance of investigating the effectiveness of the medicinal plant preparation methods used, because the active ingredients of medicinal plants can vary based on the extraction method used. In addition, medicinal plant species are also managed individually by pounding and filtering (28.30%) or brewing (16.23%).

The most common preparation method, boiling, influences the administration method of this medicinal plant. In terms of administration, almost all preparations were administered orally (77.73%) by informants in the study area (see Figure 6). These results are in accordance with [77] which was reported in Pacitan Regency, East Java, Indonesia. Kassa et al. [78] reported that oral administration offers unique advantages to practitioners of traditional medicine, allowing them to prevent complications during antidote treatment. In some cases, such as fever, whole fresh plant parts or preparations that have been pounded and then filtered (tumbuk serkai) are attached directly or compressed to the patient’s forehead. Preparations that have been boiled or brewed for inhalation of steam are given to patients who experience colds or dizziness, while diarrhoea patients generally consume P. guajava fruit directly.

3.6. Toxicity and Side Effects of Herbal Remedies

Traditional medicine, like other forms of treatment, also has potential side effects, although relatively small, and in the current study can be seen in Table 5. Results like this were also reported in research conducted in Artuma Fursi District, Amhara State, Ethiopia [79]. The existence of data on undesirable effects in traditional use is very valuable information for the clinical use of these plants in terms of safety.

The informants reported several plants such as Artocarpus altilis, Annona muricata, Ocimum basilicum, Muntingia calabura and Piper betle can cause a drowsiness effect after consuming it to treat certain diseases. However, the resulting drowsiness effect could occur due to other pharmacological activities of the plant. For example, O. basilicum has been reported to improve sleep quality and overcome insomnia in menopausal women [80].

Undesirable effects can also be caused by the use of medicinal plants that exceed the treatment dose so that they can cause side effects that are the opposite of the aim of the treatment. For example, consumption of P. guajava exceeding the dose can actually cause constipation in patients with diarrhoea [51]. This brings special attention to the importance of determining the appropriate dosage of medication and investigating the safety of the use of these medicinal plants.

All data regarding side effects were recorded based on quotes from participants, which were then analysed qualitatively. In the context of this study, ‘side effects’ refers to negative reactions or undesirable effects that may occur when consuming herbal treatments, ranging from mild symptoms such as stomach aches to more serious issues like allergic reactions, depending on the herbal formulation and individual sensitivity; essentially, these are unintended consequences of consuming herbal supplements, similar to how side effects are described in conventional medicine.

Generally, the side effects reported by participants occurred after consuming the herbal preparations they made to address several diseases related to mild COVID-19 symptoms. No further reports have been made regarding the side effects of long-term consumption. To clarify the accuracy of the reported side effects, further evaluation is necessary.