The authors of this article applied the determination of phenolic and flavonoid content in small berries to create a didactic cycle based on student-centered active learning (SCAL) in which students actively participated in the topic while studying and profile-forming as future biology and chemistry teachers. The fundamental part of the proposed didactic cycle is that students solve the following task: Determine the phenolic and flavonoid content in berries (Vaccinium myrtillus L., Vaccinium vitis-idaea L., and Vaccinium corymbosum L.) in your region. The submitted interdisciplinary topic is relevant to everyday life, and it aroused interest and enthusiasm among students. The students had the opportunity to test their theoretical knowledge in practical experimental research, and they attempted to work as researchers.

The results of epidemiological studies indicate beneficial effects of a balanced diet containing plant-based natural substances in the battle against severe diseases (Gonzalez & Riboli, 2010; Zhao et al., 2011). The protective effects are attributed to bioactive components, namely, phytochemicals (plant-based secondary metabolites), largely represented by polyphenols, and their largest subgroup called flavonoids (Silalahi, 2002; Acheampong et al., 2003). Extensive research has demonstrated many health-beneficial effects of flavonoids, including antioxidant, anti-inflammatory, cardioprotective, antimicrobial, antiviral, and anticancer effects (Birt et al., 2001; Shukla et al., 2010; Yao et al., 2011; Kapinová et al., 2017). The main sources of flavonoids in the human diet are fruits, vegetables, herbs, spices, and cereals (Liskova et al., 2019; Abotaleb et al., 2019). Bilberry (Vaccinium myrtillus L., also called European Blueberry), Mountain Cranberry (Vaccinium vitis-idaea L.), and Highbush Blueberry (Vaccinium corymbosum L.) are foods with high content of phenolic phytochemicals, tannins, procyanidins, and anthocyanidins (Brasanac-Vukanovic et al., 2018; Dróźdź et al., 2018). According to the available literature (Anastasiadi et al., 2010; Carbone et al., 2011), the content of individual subgroups of phytochemicals, including flavonoids, shows a wide variation in plant-based foods. This variation in the content of plant-based secondary metabolites in normal natural products is caused by specific conditions such as genus and species diversity, seasonal and climatic conditions, and the occurrence of microorganisms and molds.

We think that this student research topic can be an excellent experience for future biology and chemistry teachers because it is more focused on active learning and can be very motivating for students—that is, students may interact with small berries not only in supermarkets but directly in their natural home surroundings, which they know very well. This motivational aspect of the task is very important. In our application of the process, the first priority was to stimulate the situation, emphasizing that a problem is related to everyday life. As the topic has a broad focus, which requires students to apply interdisciplinary knowledge and skills, we believe it is suitable for applying the student-centered active learning approach (SCAL). Therefore, we describe the didactic cycle on this topic, which we applied at our university with future biology and chemistry teachers.

Student-Centered Active Learning

Active learning has been gaining considerable attention for several years. Currently, education is primarily focused on the development of thought operations that lead toward question formation, exploration, and verification of acquired knowledge, which leads to a deeper understanding of the investigated phenomena (Bellová et al., 2018). This process, however, requires active participation by students, ensuring an efficient development of cognitive and efficacious activities to allow students to search for solutions to any problems in theoretical and practical conditions (Bonwell & Eison, 1991).

In the frame of scientific inquiry, it is essential for students to understand the principles of scientific processes, and it is necessary to reach a deep understanding that leads to effective apprenticeship (Pavlova & Kreher, 2013; Brigati, 2018). To achieve this, an assessment is needed of the conditions leading to the active environment for this type of training (Tal & Tsaushu, 2018). The aforementioned studies agree that the process of inquiry in teaching STEM subjects (science, technology, engineering, and mathematics) should reflect realistic science as closely as possible (Ash, 2003) and that engaging in the practice of science stimulates the curiosity of students (McLaughlin et al., 2016). The inclusion of learning based on inquiry in laboratory and field courses is an effective pedagogical strategy, which supports the creativity of students. Inquiry also facilitates the integration of students within the course content and enhances the confidence of students with respect to scientific research (Asmus et al., 2019; National Research Council, 2000; Gormally et al., 2009; Jeffrey et al., 2016).

In our article, we propose and explain the didactic cycle with a focus on SCAL (student-centered active learning) for the solution to an effective interdisciplinary task. When we compiled the didactic cycle for this task, we did not use a strictly defined type of teaching method, but we did pay attention to the critical elements typical for active learning tasks with an accent on the learner (SCAL), as follows:

  • Propose a task with an appropriate level of complexity that also motivates students, generates enthusiasm, and becomes an experience for them.

  • Encourage students to develop responsibility for the solution to the task and its process.

  • Implement the process of solution by inquiry activities using discussion in class, dialogue in groups, or individual readings.

  • Create an educational environment that will encourage and stimulate the minds of students, encourage them to use their own personal experiences of previous knowledge, and create a direct connection between new and previous experience and knowledge.

Implementation of the Task

The task was assigned to master’s students studying to be biology and chemistry teachers and implemented in their elective Applied Chemistry in Botany course. The students already completed the following courses during their studies: morphology and taxonomy of higher plants; plant physiology; biochemistry; organic, analytical, and physical chemistry; laboratory technique; and statistics for biologists. We assume that the students combined the knowledge obtained from these courses while solving challenging tasks that require long-term solutions.

This study included 12 students who have been preparing to be double-subject teachers: two future teachers of biology and chemistry, five future teachers of biology and another subject, and five future teachers of chemistry and another subject. Student work was directed by two teachers: one teacher was a facilitator during the whole task, and the other teacher served as the technician and was available during the experimental phase.

Students’ Motivation

Small berry fruit is considered by many to be tasty, refreshing, delicious, and colorful. Except for polyphenols, it can be served as a source of vitamins, carotenoids, and micro- and macroelements. However, polyphenols have recently become an increasingly popular research subject because they play an important role in human health. Moreover, polyphenols are antioxidants, which prevent the formation of free radicals. Each of us should take care of our own health and try to prevent diseases. For this reason, we should know whether wild-growing plants in our local region contain natural, health-beneficial phytochemicals. This background led us to a particular formation of the tasks for students: determine total phenolic and flavonoid content in small berries growing in your local surroundings—specifically, bilberry (Vaccinium myrtillus L.), cranberry (Vaccinium vitis-idaea L.), and blueberry (Vaccinium corymbosum L.).

Theoretical Aspect of the Task

The specified task required targeted, preliminary theoretical training, planning, and scheduling for the solution processes. This was necessary to determine what students already knew about the topic and what they did not know and needed to learn.

Students, together with the guidance of the teacher, set the specific objectives of the theoretical training necessary to carry out the practical aspects of the tasks, which are displayed in Table 1. The table shows (first column) the specific objectives, which reflect students’ background knowledge, (second column) knowledge they should already have at the beginning of the task, and (third column) the expected solutions that students propose to complete the task. A full description of the didactic cycle is shown in Figure 1 and corresponds to the activities presented in Table 1, where it can be seen when the students were working individually and when they were divided into groups.

Table 1.

Concretization of the objectives of the given task. The table shows (first column) the specific objectives, which reflect students’ background knowledge, (second column) knowledge they should already have at the beginning of the task, and (third column) the expected solutions that students propose to complete the task.

Specific ObjectivesStudents’ Initial Findings and Necessary SkillsExpected Solution
Characterize the morphology of Vacciniaceae family Morphology of higher plants
Taxonomy of higher plants 
Morphological description: Vaccinium myrtillus L., Vaccinium corymbosum L., Vaccinium vitis-idaea L. 
Describe the influence of active substances on human health Substances essential to life and factors influencing human health Characteristic of antioxidants 
Define, classify phenolic compounds Organic chemistry of natural products Characteristics of polyphenols and flavonoids 
Characterize the distribution of berries and choice of collection areas Geographical knowledge of the region Carry out the collection of berries 
Suggest analytical methods for the determination of total phenolic and flavonoid content determination Physics and chemistry of quantitative determinations Suggest quantitative determination of polyphenols and flavonoid according to lab facilities 
Prepare spectrophotometer Cintra for determination Instrumental operation skills Instrumental preparation 
Prepare sample extracts for determination, execute quantitative determination of polyphenols and flavonoid, and process the results Practical skills of separation methods, ICT skills Sample preparation, measurement execution, calibration curve creation, determination of total phenolic and flavonoid content according to calibration curve 
Compare the results of wild and purchased berries ICT skills, statistical skills Supplemental Material 2 
Verification of research results Self-study Comparison with literature 
Formation of research conclusions Reasoning of findings Interpretation of findings and discussion 
Specific ObjectivesStudents’ Initial Findings and Necessary SkillsExpected Solution
Characterize the morphology of Vacciniaceae family Morphology of higher plants
Taxonomy of higher plants 
Morphological description: Vaccinium myrtillus L., Vaccinium corymbosum L., Vaccinium vitis-idaea L. 
Describe the influence of active substances on human health Substances essential to life and factors influencing human health Characteristic of antioxidants 
Define, classify phenolic compounds Organic chemistry of natural products Characteristics of polyphenols and flavonoids 
Characterize the distribution of berries and choice of collection areas Geographical knowledge of the region Carry out the collection of berries 
Suggest analytical methods for the determination of total phenolic and flavonoid content determination Physics and chemistry of quantitative determinations Suggest quantitative determination of polyphenols and flavonoid according to lab facilities 
Prepare spectrophotometer Cintra for determination Instrumental operation skills Instrumental preparation 
Prepare sample extracts for determination, execute quantitative determination of polyphenols and flavonoid, and process the results Practical skills of separation methods, ICT skills Sample preparation, measurement execution, calibration curve creation, determination of total phenolic and flavonoid content according to calibration curve 
Compare the results of wild and purchased berries ICT skills, statistical skills Supplemental Material 2 
Verification of research results Self-study Comparison with literature 
Formation of research conclusions Reasoning of findings Interpretation of findings and discussion 
Figure 1.

Didactic interpretation cycle.

Figure 1.

Didactic interpretation cycle.

Together with teachers, the students evaluated the acceptable solutions of the theoretical training and set particular objectives for the exploratory-practical aspects:

  • Describe the occurrence of berries and define the areas of collection.

  • Quantitatively determine the total phenolic content (TPC) by a Cintra 202 spectrophotometer.

  • Quantitatively determine the total flavonoid content (TFC) by a Cintra 202 spectrophotometer.

  • Compare different wild and commercially cultivated samples.

  • Compare obtained results with results previously published in the literature.

The students divided themselves into two groups (biologists and chemists) based on their own judgments about their knowledge, skills, and abilities. The first group, the future biologists, represented students who leaned more toward botany or physiology of plants; the second group, the future chemists, represented students who leaned more toward physical chemistry and had stronger skills in methodologies of analytical measurements. Prior to the task, students had the opportunity to gain new knowledge from studying domestic and foreign literature and internet resources. The future biologists studied, in detail, the features of phenolic substances and flavonoids, their impacts on human health, and the characteristics of the Vacciniaceae family. The future chemists researched the methodology of measurement, spectral methods for the determination of polyphenols and flavonoids, and the methods of sample preparation. The students determined the following in group discussion: the area of investigation, the species to be studied, the device to be used, and the type of methodology to be applied. Then, the students exchanged their information across groups, identified areas of berry collection, and decided when to conduct their work. Through these activities, students were able to evaluate their teamwork and engaged in dialogue and discussion, leading to beneficial cooperation.

Experimental Part of the Task

At the beginning of the students’ work, it was important to compare the occurrence of berries in Slovakia with the selection of areas for collection. This part was very interesting for the students because they utilized their geographical knowledge of well-known surroundings and arranged the collection in pairs to accelerate the process.

The fruits (Vaccinium myrtillus L., Vaccinium corymbosum L., and Vaccinium vitis-idaea L.) were collected from different parts of Slovak mountain ranges (samples 1–10), and five samples were purchased in independent supermarkets (samples 11–15; Brigitta Blue).

Before the experimental part, a joint discussion was conducted by the teacher-technician about safety in the laboratory.

In the experimental part, the students divided themselves into mixed groups without regard to biologist and chemist roles and carried out measurements in a biochemical laboratory. The students were guided by both teachers (teacher and teacher-technician) and had the opportunity to work with the Cintra 202 spectrophotometer (accompanied with Cintral software, working wavelengths ranged from 190 to 1200 nm). The methodology utilized by the students followed the theoretical training presented by the teacher. One group determined the total phenolic content, and the other group determined the total flavonoid content. For those interested in the methodology of the measurement itself (including the determination of total phenolic content and flavonoid content), full details are available in the Supplemental Material with the online version of this article.

After finishing their experimental work, students constructed for both standards a calibration curve and calculated its equation by least squares. The obtained polyphenol and flavonoid concentration values were statistically treated. Students presented their results in tables and graphs and then compared results in a joint discussion. These are available in the Supplemental Material.

The experimental aspect of the research revealed that the total phenolic content in wild blueberries (Vaccinium myrtillus L.) is significantly higher than in wild cranberries (Vaccinium vitis-idaea L.). The total flavonoid content measurements showed insignificant differences. In both cases, the total phenolic and flavonoid contents were lowest in purchased samples, which were grown in controlled conditions.

Within the group process, the students explained to each other new ideas or common rationale of measurement results and additional procedures. Subsequently, the students, together with the teacher, evaluated the results of each group and formulated measurement conclusions. Since the research work of scientists requires reliable results, the students were also required to compare their results with measured values published in literature. They concluded that the measured results were comparable to the results of previous authors who conducted similar research in different countries (geographically and climatologically similar) (Borowska et al., 2009; Marinova et al., 2005; Bunea et al., 2011).

The final phase was a presentation of student results and conclusions in which students discussed their specific measurements and findings. The students also expressed their opinions and attitudes about the process of solving the task and assessed their achievements mutually. The teacher evaluated the overall work and the work of each group.

Student Feedback

During final presentations, the students expressed their satisfaction with the process of the task and positively evaluated the freedom of planning and minor interventions of the teacher; however, the students appreciated the teacher’s helpfulness during the choice of methods, measurements, and evaluation of the results.

Most students liked this topic; it enhanced their interests and prompted further questions, not only from the aspect of comparing the phenolic content in different foods but also from the aspect of the medical effects of phytochemicals. For those reasons, students expressed their interest in extending the research and developing it in their final master’s theses because the didactic model helped them test their own research work abilities.

The combination of group work and individual knowledge was also very beneficial for students. It was revealed that team study can be a valuable experience for students if they work together in innovative surroundings while simultaneously forming verbal and other communication skills within the team.

The students also positively evaluated the interdisciplinary nature of the chosen topic because they could use knowledge and skills not only from biology and chemistry but also from IT, mathematics, and geography.

Student-centered active learning (SCAL) motivates students to create their own observations, inquiries, and conclusions toward a better understanding of scientific principles and methods. It is possible to apply this didactic cycle in other STEM courses, mainly in topics that require preliminary in-depth theoretical training and utilize students’ interdisciplinary knowledge and skills.

Today, there is a strong need for further measurements and comparison of total phenolic and flavonoid content values in different kinds of berries from various geographical and climatological conditions. Considering the increasing incidence of diseases affecting humans, this topic is highly relevant today: phytochemicals play an important role in maintaining good health and strengthening human immunity, and long-term consumption of plant-based foods with high polyphenol and flavonoid content could play a key role in preventing and ameliorating diseases.

In the topic presented here, one that relates to everyday life, students developed their scientific abilities and improved their biological, chemical, and informational literacy due to the interdisciplinary nature of the task. If we want to shape future teachers of biology and chemistry, science education should move in this direction—encouraging students to work as scientists, to help create their educational environment, and to improve their professional knowledge.

The following are available with the online version of this article:

  • Methodology of the measurement (Determination of total phenolic content; Determination of total flavonoid content)

  • Measurement results

This work was supported by the Agency of Faculty of Education [GAPF] under Grant [3/1a/2021] and the Scientific Grant Agency of the Ministry of Education, Science, Research and Sport of the Slovak Republic and the Slovak Academy of Sciences [VEGA] under Grant [1/0128/21].

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