A Review on Active Compounds : Chemistry Behind Tea, Coffee, Chocolate

Abstract

This review synthesizes current scientific understanding of the principal active chemical constituents found in tea, coffee, and cocoa or chocolate, emphasizing their biochemical activities, production-related chemical transformations, comparative chemistry, and sustainable or green chemistry implications. These three globally consumed plant-derived beverages share several bioactive chemical families that contribute not only to their unique sensory profiles but also to diverse physiological effects in humans. Tea, derived from the leaves of Camellia sinensis, is particularly rich in polyphenolic catechins, including epigallocatechin-3-gallate (EGCG), which play major roles in antioxidant and anti-inflammatory mechanisms. Alongside these, L-theanine and caffeine contribute to the neuroactive and psychostimulant properties of tea, influencing cognitive performance, relaxation, and metabolic regulation. Chemical modifications during fermentation or oxidation, such as in black and oolong teas, lead to complex products like theaflavins and thearubigins, significantly altering their bioavailability and physiological potency. Coffee, one of the most widely traded commodities, contains caffeine, chlorogenic acids, trigonelline, and roasting-derived compounds such as melanoidins and diterpenes (cafestol and kahweol). These constituents exhibit both beneficial and dose-dependent effects on cardiovascular, metabolic, and neurological health. The brewing method, degree of roasting, and bean variety critically determine the chemical profile and antioxidant capacity of coffee, intertwining sensory quality with potential health outcomes. Cocoa and dark chocolate, derived from Theobroma cacao, contain abundant flavanols (catechin, epicatechin), proanthocyanidins, and methylxanthines, primarily theobromine with minor caffeine content. Post-harvest fermenting, drying, and roasting steps induce profound structural and quantitative changes in these polyphenols, influencing their absorption and physiological activity. While moderate cocoa consumption supports vascular function and endothelial health, heavy processing can diminish its beneficial compounds.Comparative analysis reveals that polyphenols and methylxanthines across tea, coffee, and cocoa form overlapping chemical frameworks, sharing similar structural motifs and biological mechanisms involving reactive oxygen species scavenging, nitric oxide regulation, and adenosine receptor modulation. However, their in vivo effects depend on complex interactions between molecular structure, food matrix, processing, and individual genetic or microbiome-related factors. Furthermore, the review identifies promising green-chemistry strategies to enhance sustainability and bioactive preservation. These include water- or enzyme-assisted extraction, recycling of processing by-products such as coffee pulp or cocoa husks, and energy-efficient roasting technologies. Together, these insights provide an integrative chemical foundation to guide future studies on health impacts, processing optimization, and circular utilization of tea, coffee, and cocoa resources.

Introduction

Tea, coffee, and cocoa are globally consumed products valued for their flavor and significant health benefits, which arise mainly from bioactive secondary metabolites such as polyphenols and methylxanthines. Tea (Camellia sinensis) is rich in catechins—especially EGCG—along with caffeine and L-theanine, contributing to antioxidant activity, calm alertness, and cardiovascular benefits. Coffee (Coffea spp.) is characterized by caffeine and chlorogenic acids, whose levels and sensory effects are strongly shaped by roasting through Maillard and caramelization reactions. Cocoa (Theobroma cacao) contains high levels of flavanols, procyanidins, and theobromine, offering vascular, neurocognitive, and mood-related benefits, while cocoa butter defines chocolate’s unique texture.

Processing steps—such as fermentation, oxidation, roasting, and brewing—play a critical role in transforming these compounds, influencing flavor, bioavailability, and health effects. Across all three commodities, polyphenols and methylxanthines show antioxidant, anti-inflammatory, cardioprotective, metabolic, neuroprotective, and gut-microbiota–modulating effects, though excessive intake (especially caffeine or sugar-rich chocolate) carries risks.

The review highlights growing interest in green chemistry and sustainable extraction, including ultrasound- and microwave-assisted extraction, supercritical CO?, and natural deep eutectic solvents, which improve yield, preserve sensitive compounds, and enable waste valorization (e.g., spent coffee grounds, cocoa shells). While these methods offer environmental and economic advantages, challenges remain in scalability, compound stability, solvent recovery, and standardization.

Conclusion

Applying green chemistry to extraction and processing of bioactives from tea, coffee and cocoa is both feasible and beneficial.Here are some practical steps for researchers and industries. 1) Prioritize low-temperature, solvent-efficient techniques (UAE, MAE) with food-grade solvents (ethanol/water, NADES where food-safe). 2) Use scCO? for defatting or nonpolar separation steps when solvent-free extracts are required. 3) Valorize agro-residues (spent coffee grounds) as feedstocks to improve economics and reduce waste. 4) Integrate purification techniques that minimize solvent exchange (resins, membranes) and design for solvent recycling.

References

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Copyright

Copyright © 2026 Falguni Bhavsar, Mitesh Agrawal, Saurabh Rakhonde, Ayush Karmore. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.