Analytical tools for students to study anthocyanins and carotenoids from autumn leaves

Previous studies have shown that students’ interest in botany tends to decrease with age, but interest in topics of microscopic level such as DNA and proteins increases [1]. To test students’ knowledge of plant chemistry we asked Finnish secondary school students (N=41) to list compounds or compound groups in plants. Majority of them could name only water and glucose. To increase student knowledge and interest in plant chemistry, we have created an inquiry task where students study the anthocyanins and carotenoids of autumn leaves utilizing both simple and more sophisticated analytical methods.

The first steps of the task include the extraction of anthocyanins and carotenoids from the leaves, and the separation of these compounds into different phases by liquid-liquid extractions. These steps can be performed in a regular secondary school laboratory using student collected samples. From the separated phases, the amount of pigments are quantified spectrophotometrically. Finally, the anthocyanins are analyzed by a rapid and simple UPLC-MS/MS method to discover if the sample contains delphinidin, cyanidin, pelargonidin, peonidin, petunidin or malvidin type anthocyanidin derivatives.

The task was tested with 18 secondary school students and 16 university students. Based on the feedback, students enjoyed both the extraction, which is visually impressive because of the colorful extracts, as well as the sample collection. Comparing students’ results with results determined by a trained chemist showed that the student groups could carry out the analyses reliably.

• References

• 1 Baram-Tsabari A, Sethi RJ, Bry L, Yarden A. Identifying students’ interests in biology using a decade of self-generated questions. Eurasia J Math Sci Technol Educ 2010; 6: 63-75.