Impact of Moderate Cold and Salt Stress on the Accumulation of Antioxidant Flavonoids in the Leaves of Two Capsicum Cultivars.

Max Daniel Dicke,Björn Usadel,Anika Wiese-Klinkenberg,Alexandra Wormit,Alexander Putz,Laura Verena Junker-Frohn,Björn Thiele,Andrea Neuwohner,Franziska Genzel

doi:10.1021/acs.jafc.1c00908

Abstract

The horticultural production of bell peppers generates large quantities of residual biomass. Abiotic stress stimulates the production of protective flavonoids, so the deliberate application of stress to the plants after fruit harvest could provide a strategy to valorize horticultural residuals by increasing flavonoid concentrations, facilitating their industrial extraction. Here we exposed two Capsicum cultivars, a chilli and a bell pepper, to cold and salt stress and combinations thereof to determine their valorization potential. Noninvasive image-based phenotyping and multiparametric fluorescence measurements indicated that all stress treatments inhibited plant growth and reduced the leaf chlorophyll fluorescence index, with the chilli cultivar showing greater sensitivity. The fluorescence-based FLAV index allowed the noninvasive assessment of foliar luteolin glycosides. High-performance liquid chromatography-mass spectrometry (HPLC-MS) analysis showed that moderate cold increased the levels of two foliar antioxidant luteolin glycosides in both cultivars, with bell pepper containing the highest amounts (induced to maximum 5.5 mg g-1 DW cynaroside and 37.0 mg g-1 DW graveobioside A) after combined stress treatment. These data confirm the potential of abiotic stress for the valorization of residual leaf biomass to enhance the industrial extraction of antioxidant and bioactive flavonoids.

Highlights

The increasing human need for plants and plant-derived compounds has encouraged the intensified agricultural production of food, feed, and biomass crops, as well as medicinal and aroma plants
Bell pepper (Capsicum annuum L.) is a crop plant grown for its fruits, which provide a good source of vitamins, carotenoids, and phenylpropanoids.[5]
The plants were cultivated in growth chambers (Hühren Kalte-Klima-Elektrotechnik, Erkelenz, Germany) under the following conditions: 24 °C/18 °C day/night temperature, 10 h photoperiod, 300 μmol m−2 s−1 light provided by metal halide lamps, and 55% relative humidity

Summary

Introduction

The increasing human need for plants and plant-derived compounds has encouraged the intensified agricultural production of food, feed, and biomass crops, as well as medicinal and aroma plants. The agriculture, horticulture, and food/feed industries generate large amounts of waste biomass.[1] The sustainable use of such biomass residuals adds industrial value and contributes to the efficient utilization of resources. Most waste biomass is converted into energy or biogas,[2] but there is increasing interest in the use of residual green biomass as a source of high-value secondary metabolites.[3,4] Bell pepper (Capsicum annuum L.) is a crop plant grown for its fruits, which provide a good source of vitamins, carotenoids, and phenylpropanoids.[5] the leaves of pepper plants contain valuable bioactive compounds, such as the antioxidant flavonoids cynaroside (luteolin-7-glucoside), graveobioside A

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