1. Introduction
Plants have the particularity of having a very large reservoir of potential bioactive compounds [1]. They may contain harmful substances such as heavy metals absorbed from the soil [2]. In West Africa, particularly Cote d’Ivoire, Hibiscus sabdariffa is used by local units to produce consumer products made from the plant’s dried flowers, commonly known as “bissap” [3]. The non-quality of consumer products not only caused a loss of around 17 billion CFA francs to the Ivorian economy between 2016 and 2023, but also posed a serious threat to consumer health [4]. To reduce the impact of this non-quality, the government has set up the National Committee to Combat Counterfeiting (CNLC) [4]. Therefore, due to a lack of knowledge about quality control of dried bissap flowers and in order to support the NCLC, the objective of our study was to contribute to the quality control of “Kuinafo” brand bissap flowers, popular among the population and produced locally for the preparation of herbal teas. The literature makes no mention of studies on the characterisation of bissap flowers produced in the north of Côte d’Ivoire and the need to protect the health of consumers (by analysing the heavy metals) of this product by drawing up an Ivorian standard.
2. Materials and Methods
2.1. Method for Determining Heavy Metals and Minerals
The determination of heavy metals (Hg, Ars, Cd and Pb) and minerals (Fe, Ca and K) is carried out using the AOAC 999.11 method, which is characterised by three (3) stages.
Step 1/3: Mineralisation of the sample
2 g of dried plant flowers were placed in the oven to dry at 102˚C to 105˚C for 1 hour. After cooling in the desiccator, the sample was heated in an oven using a temperature gradient. 250˚C for 2 hours, then 550˚C for 4 hours.
Step 2/3: Preparation of standard solutions
It begins with the preparation of a standard range of 0.5 mg/l, 1 mg/l, 3 mg/l and 6 mg/I from a standard solution of 1000 mg/l. This is done for each heavy metal and mineral to be measured. The calibration line is checked with a quality control (QC) of 5 mg/l. The standard solutions were used to draw the calibration lines needed to determine the concentration of the chemical elements considered by the Beer-Lambert law.
Step 3/3: Dosage
The ash obtained in the mineralisation step was recovered with 2 ml of 0.1 N hydrochloric acid in a 50 ml flask. Distilled water was added up to the mark. The mixture obtained is taken to an atomic absorption spectrophotometer (AAS) to determine the element in question.
2.2. Method for Determining Ash Content
The ash content indicates the proportion of minerals in our sample. Its determination involves several stages.
Step 1/2: Obtaining the ash
2 g of dried bissap flowers are weighed into a tared crucible. The mixture is baked in an oven at 550 C for 4 hours.
Step 2/2: Calculating the ash content
After cooling in a desiccator for 45 minutes, the crucible is weighed and the ash content is calculated using the following formula:
With M0: weight of the empty crucible. M1: weight of the crucible + test sample. M2: weight of crucible + calcined residue.
The level represents the mineral fraction of bissap. This fraction can be composed of mineral salts such as calcium, potassium, sodium and various trace elements (Ouadfel S, 2018).
2.3. Method for Determining Moisture Content
The moisture content is used to assess the product’s suitability for preservation. It is determined in 2 stages.
Step 1/2: Drying
The empty crucible and the 2 g of sample are weighed. The crucible and the weighed sample are placed in an oven at 103 ± 2 C for 1 hour.
Step 2/2: Calculating the moisture content
After cooling in a desiccator for 45 minutes, the crucible is weighed and the moisture content is calculated using the following formula :
With H: water content expressed as a percentage; MO: mass (g) of the empty crucible; M1: mass (g) of the empty capsule + test sample before heating; M2: mass (g) of the empty capsule + test sample after heating.
3. Results
3.1. Results for the Determination of Heavy Metals
Table 1 presents the content of heavy metals studied in the bissap flower sample.
Table 1. Heavy metal contents in our sample.
Parameters |
Results (mg/Kg of dried flowers) |
Standards (μg/Kg(b.w.)/dr) |
Arsenic (As) |
<1 |
0.3 (US EPA) |
Cadmium (Cd) |
0.18 |
0.35 (EFSA) |
Mercury (Hg) |
<1 |
0.5 (EFSA) |
Lead (Pb) |
1.310 |
0.3 (ANSES) |
3.2. Results for Mineral Determination
Table 2 presents the content of minerals studied in the bissap flower sample.
3.3. Results for Determining Ash Content
The ash content is the mineral fraction in bissap flower samples. The ash content determined in our sample was 9.39 ± 0.05%.
Table 2. Mineral content in our sample.
Parameters |
Units |
Results |
Standards (WHO/FAO, 2004) |
Calcium (Ca) |
g/100g |
1.79 |
769 mg/day |
Iron (Fe) |
mg/Kg |
172.71 |
6 mg/day |
Potassium (K) |
g/100g |
1.76 |
2000 mg/day |
3.4. Results for Determining Moisture Content
The water content is the fraction of water in the bissap flower samples. The water content measured in our sample was 7.21 ± 0.02%.
4. Analysis
The lead content measured in our sample was 1.310 mg/kg of dried Hibiscus sabdarrifa flowers. The ANSES standard sets a maximum daily amount at 0.3 ug/kg (of body weight). Tiani et al. [5], obtained a value of 0.69 mg/kg from dried Hibiscus sabdarrifa flowers. This value is lower than ours. Since the ANSES standard sets a maximum daily quantity of 0.3 μg/kg (of body weight), for example, an adult weighing 60 kg would need to consume at least five (5) sachets (one sachet contains 3 g of dried Hibiscus sabdarrifa flowers) of Hibiscus sabdarrifa herbal tea over the course of the day for his or her health to be at risk.
The cadmium value obtained in our study was 0.18 mg/kg of dried Hibiscus sabdarrifa flowers. The EFSA standard defines a maximum daily intake of 0.35 ug/kg (of body weight). The value of 0.67 mg/kg of dried flowers obtained by [5] in their study on Hibiscus sabdarrifa flowers is higher than ours. This difference could be explained by the fact that Hibiscus sabdarrifa flowers are harvested from a plot (Gounti Valley) not far from a landfill area and small industries in Niger; these areas being known sources of lead [6]. As with lead, if these figures are based on a consumer’s weight, they would have to consume more than ten (10) sachets (one sachet contains 3 g of dried Hibiscus sabdarrifa flowers) of Hibiscus sabdarrifa tea to be exposed to cadmium.
The mercury analysis in our study yielded 0.5 mg/kg of dried Hibiscus sabdarrifa flowers. The EFSA standard sets a maximum daily amount at 0.5 ug/kg (of body weight). The weight of the consumer must be taken into account. For example, an adult weighing 60 kg would need to consume at least ten (10) sachets (one sachet contains 3 g of dried Hibiscus sabdarrifa flowers) of Hibiscus sabdarrifa tea over the course of the day for his or her health to be threatened by the presence of mercury.
For arsenic, a value of less than 1 mg/kg of Hibiscus sabdarrifa flowers was determined. The US EPA standard sets a maximum daily intake of 0.3 μg/kg (of body weight). An adult weighing 55 kg would, therefore, need to consume at least five (5) sachets (one sachet contains 3 g of dried Hibiscus sabdarrifa flowers) of Hibiscus sabdarrifa tea per day for the daily arsenic dose to be exceeded.
In particular, the manufacturer should draw up a table of data suggesting the maximum daily quantity of herbal tea permitted, and make it available to consumers to warn them of any adverse effects of heavy metals on health.
Given the accumulation of heavy metals in the body (a long-term threat to consumer health), the quantities of dried flowers used for herbal tea should be respected [7].
The potassium content measured was 1.76 g/100g (i.e. 0.05 g/sachet of Hibiscus sabdarrifa herbal tea). As the WHO health safety limit is 2 g/day, our sample does not present any danger to consumers. The value obtained is close to that found by [8] in their study of bissap flowers, which was 2.02 g/100g. The study focused on traditional pharmacopoeia [8]. This may be due to the proximity of the production areas in northern Côte d’Ivoire and Mali.
Calcium is a substance involved in bone mineralisation. Its content in our sample of Hibiscus sabdarrifa flower is 1790 mg/100g (i.e. 53.7 mg/sachet of Hibiscus sabdarrifa tea). A sachet of Hibiscus sabdarrifa tea does not meet the average nutritional requirement for calcium, which the WHO/FAO (2004) estimates at 769 mg/day. The value obtained in our study is close to that of Kerharo and Adam (1583 mg/100g) who carried out work on bissap flowers [8]. The value obtained calcium levels of 3 mg/100g of dried bissop flowers in Asia [9]. These values, which differ from ours, could be explained by various factors such as soils and climatic conditions, which differ from one continent to another.
The iron content determined in our sample was 172.71 mg/kg (i.e. 0.5 mg of iron per sachet of Hibiscus sabdarrifa tea). The standard is set at 6 mg/day by the French Food Safety Agency. The value obtained is different from that of 8330 mg/kg (of dried flowers), obtained by [10]. This difference could be explained by various factors such as cultivation practices.
The results of the ash content showed values of 9.49% in our study. This value differs from the 6.9% obtained by Mahadevan et al. (2008) in their studies of bissap flowers in Asia. The differences observed could be due to factors such as growing conditions and the country of origin of the bissap flowers (Morton et al. 1987).
The water content in our sample was 7.21%. This value complies with the standard, which sets the water content at less than 15% (CODEX standard 154-1985). The authors, in their work on Hibiscus sabdarrifa flowers, obtained a value of 9% [9]. This is in line with ours. The low water content obtained in our sample means that there is less risk of micro-organisms developing, thus ensuring good preservation of the product.
5. Conclusions
People consume dried Hibiscus sabdarrifa flower tea. The physico-chemical analysis of Kuinafo brand bissap, produced and sold on the local market, showed that apart from lead, the heavy metals (Ars, Hg and Cd) were in compliance with standards. In addition, dried bissap flowers had significant nutritional value (iron, calcium and potassium) and the low water content measured in the sample favoured the preservation of bagged Hibiscus sabdarrifa flowers in the form of herbal tea. The study highlighted the importance of quality control for Hibiscus sabdarrifa-based herbal teas in order to prevent any adverse effects that this product might have on consumer health.
We suggest that Ivorian bissap quality control standards be drawn up, as the characteristics of this plant vary from one region to another. This standard would be adapted to local realities and would make it possible to objectively determine the quality of bissap. The standard could, for example, define the permitted carbohydrate content (to determine, for example, whether it should be consumed by diabetics), pH (to assess its acidity), protein, vitamin C or fat content (nutritional values).
It would be wise to define the maximum daily quantities of sachets that can be used to prepare herbal teas on the product packaging, according to the weight of the consumer, in order to protect the consumer’s health.