Beyond the Rhizome: Phytochemistry, Biological Activities, and Sustainable Utilization of Curcuma longa L.

Curcuma longa L. (turmeric) is an economically and medicinally important species widely utilized as a spice, traditional medicine, and source of bioactive compounds. Although research and commercial exploitation have predominantly focused on the rhizome and its major curcuminoids, evidence increasingly shows that other plant parts also contain chemically diverse and biologically active constituents. This review integrates current knowledge of the botany, traditional uses, phytochemistry, pharmacological activities, industrial applications, and sustainable utilization of C. longa, with particular emphasis on whole plant utilization. Unlike previous reviews that have largely focused on the rhizome and curcuminoids, this review synthesizes evidence across underutilized plant organs and links their tissue-specific phytochemistry with biological activities, industrial applications, and circular-bioeconomy potential. Rhizomes are rich in curcuminoids and turmerone-dominated essential oils, whereas leaf, flower, root, and root tuber contain diverse phenolics, flavonoids, terpenoids, and other specialized metabolites. However, these non-rhizome tissues remain substantially less studied, and their distinct phytochemical and functional value has not yet been systematically established. Preclinical studies have linked these constituents to antioxidant, anti-inflammatory, antimicrobial, antiviral, anticancer, antidiabetic, hepatoprotective, and wound-healing effects. However, clinical evidence remains variable across these activities. Beyond therapeutic applications, underutilized aerial parts and processing residues may serve as source of essential oils, natural preservatives, fibers, biodegradable materials, fermentation products, and bioenergy. Cascading biorefinery approaches that integrate tissue-specific phytochemistry may broaden turmeric utilization beyond the rhizome, reduce agricultural waste, and contribute to circular-bioeconomy development. Further research should prioritize underexplored plant organs, standardized phytochemical characterization, safety assessment, well-designed clinical studies, and techno-economic and life-cycle assessments.