CHAPTER TWO LITERATURE REVIEW
2.1 Background of the Study
The guava plant (Psidium guajava L.), a member of the Myrtaceae family, is a tropical evergreen shrub widely valued for its rich array of secondary metabolites with significant medicinal properties. These bioactive compounds are predominantly found in the leaves, fruit peel, bark, and roots (Kumar et al., 2021). Guava leaves and fruits contain high concentrations of flavonoids such as quercetin, guaijaverin, kaempferol, and avicularin, which exhibit strong antioxidant activity by scavenging free radicals and mitigating oxidative stress linked to chronic diseases, including diabetes and cardiovascular disorders (Huynh et al., 2025). Phenolic acids, notably gallic acid, ellagic acid, caffeic acid, and ferulic acid, contribute to its anti-inflammatory effects through inhibition of pro-inflammatory enzymes such as COX-2 and modulation of cytokine production, supporting its traditional use in managing gastrointestinal disorders, arthritis, and wound healing (Sahal, 2025).
Tannins and saponins present in guava demonstrate potent antimicrobial properties by disrupting bacterial cell membranes, effectively inhibiting pathogens such as Staphylococcus aureus and Escherichia coli, which explains its longstanding traditional application against infections and diarrhea (Al-Rimawi, 2025). Terpenoids, including β-caryophyllene, limonene, and caryophyllene oxide, along with essential oils, possess analgesic, anticancer, and antidiabetic activities through mechanisms such as induction of apoptosis in cancer cells, modulation of pain pathways, and enhancement of insulin sensitivity (Zou, 2023). Furthermore, the high ascorbic acid (vitamin C) content in guava enhances immune function and collagen synthesis, with synergistic interactions among these metabolites amplifying the plant’s overall therapeutic potential (Butt, 2025).
Despite substantial in vitro and preclinical evidence supporting the antioxidant, antimicrobial, anti-inflammatory, antidiabetic, and anticancer properties of guava’s secondary metabolites, several critical research gaps continue to hinder their clinical translation and commercial exploitation (Ugbogu et al., 2022). Chief among these is the scarcity of large-scale, randomized controlled human clinical trials to confirm efficacy, determine optimal dosage, evaluate long-term safety, and establish therapeutic outcomes in diverse populations (Tousif et al., 2022). Additionally, significant variations in metabolite composition due to regional, environmental, soil, and cultivar differences remain underexplored, limiting the identification of superior chemotypes for standardized pharmaceutical or nutraceutical development (Emam, 2025).
The influence of different extraction methods, processing techniques, and strategies to improve bioavailability on the stability and absorption of these bioactive compounds has also received insufficient attention, constraining the development of reliable formulations (Sahal, 2025). Furthermore, limited research exists on the synergistic mechanisms among guava’s secondary metabolites, potential drug-herb interactions, toxicity profiles across populations, and the valorization of processing by-products through metabolomics approaches (Huynh et al., 2025).
Addressing these gaps through advanced clinical research, metabolomics studies, and interdisciplinary trials is essential to bridge traditional medicinal uses with evidence-based medicine, thereby unlocking the full therapeutic and economic potential of guava as a sustainable medicinal plant resource.
References (APA 7th Edition)
Al-Rimawi, F. (2025). Evaluation of antimicrobial efficacy of Psidium guajava L. leaf extract. Scientific Reports.
Butt, E. (2025). Guava (Psidium guajava): A brief overview of its therapeutic and health benefits. Journal of Medicinal Plants Research. (In press)
Emam, Y. (2025). Metabolomics in guava: Quality traits, composition, applications. Phytochemistry Reviews.
Huynh, H. D. (2025). Bioactive compounds from guava leaves (Psidium guajava L.). Molecules, 30(6), 1278.
Kumar, M., Saurabh, V., Tomar, M., Hasan, M., Changan, S., Prakash, S., Berwal, M. K., … & Sharma, S. (2021). Guava (Psidium guajava L.) leaves: Nutritional composition, phytochemical profile, and health-promoting bioactivities. Foods, 10(4), 752.
Sahal, A. (2025). A comprehensive review on the nutritional composition, bioactive compounds, and encapsulation of guava leaves. Food Chemistry Advances.
Tousif, M. I., Nazir, M., Saleem, M., Bashir, S., & Shafiq, N. (2022). Psidium guajava L.: An incalculable but underexplored food crop—Its phytochemistry, ethnopharmacology, and industrial applications. Molecules, 27(20), 7016.
Ugbogu, E. A., Akubugwo, E. I., Ude, V. C., & Emmanuel, O. (2022). The ethnobotanical, phytochemistry and pharmacological activities of Psidium guajava L. Arabian Journal of Chemistry, 15(5), 103753.
Zou, X. (2023). Meroterpenoids bioactivity from guava (Psidium guajava L.) review. Advances in Traditional Medicine.
