Papaya

Botanical Profile

Note on species differentiation: Sweet orange (Citrus sinensis) and bitter orange (Citrus × aurantium) should be considered separately in botanical and phytochemical statements.

Carica papaya is a tropical fruit plant of the Caricaceae with a herbaceous to tree-like growth habit, large palmately lobed leaves and ovoid to pear-shaped fruits. From a raw-material perspective, fruit, latex, leaves, seeds and enzyme fractions must be clearly distinguished.

Carica papaya L. is a fast-growing, usually unbranched to weakly branched tropical plant with a soft trunk, spirally arranged large long-petiolate leaves and latex-bearing tissue. The leaves are deeply palmately lobed and borne on long petioles. The species forms male, female or hermaphroditic flowers; these develop into large fleshy berry fruits with orange to reddish pulp and numerous black seeds in the central fruit cavity. The unripe fruit is used as a vegetable and the ripe fruit as a sweet fruit. The latex-rich sap of unripe fruits is the classic source of proteolytic enzymes, particularly papain and chymopapain. Leaves, seeds and fruit pulp each represent distinct raw-material types with different constituent profiles.

Phytochemistry

Papaya fruits contain water, sugars, organic acids, carotenoids, dietary fibre, minerals and vitamin-rich fractions. The orange pulp is characterised by carotenoids such as beta-cryptoxanthin, beta-carotene and lycopene, with proportions varying by cultivar. The latex of unripe fruits contains proteolytic enzymes such as papain, chymopapain and other cysteine proteases. Papaya seeds contain pungent-bitter components, fatty oil, glucosinolate- or isothiocyanate-related substances such as benzyl isothiocyanate, as well as accompanying phenolic compounds. Leaves contain flavonoids, phenolic acids, alkaloid and enzyme fractions and other polar plant constituents. Composition and technological properties depend strongly on maturity, plant part, cultivar, climate, drying and extraction.

Traditional Uses

Carica papaya is deeply rooted in tropical regions as a food, culinary and household plant. Ripe fruits are eaten fresh, while unripe fruits are cooked, fermented or used as vegetables. The latex-rich sap of unripe fruits was traditionally used for tenderising meat and for enzymatic applications. Seeds are regionally used as a pepper-like pungent raw material, while leaves are described in various tropical traditions as a bitter-astringent botanical raw material. In ethnobotanical contexts, fruit, leaf, seed and latex are used in clearly different ways. Such historical patterns of use must be distinguished from modern medical assessments and permitted health-related claims.

Current Research

Research on Carica papaya covers fruit quality, carotenoids, proteolytic enzymes, seed constituents, leaf chemistry and agronomic topics. Papain is technologically important and is studied in food processing, analytics, biochemistry and industrial applications. Leaf extracts are investigated in experimental studies, including cell and animal models and limited clinical contexts, particularly in relation to haematological and inflammation-related questions; however, the evidence varies depending on the question. Seeds and latex are studied for their pungent-bitter and enzymatic components. For assessment, it is essential to distinguish whether fruit, leaf, seed or latex is being considered, as these raw materials are not interchangeable chemically or in terms of safety.

Sources

• Plants of the World Online: Carica papaya L.; Royal Botanic Gardens, Kew.
• Britannica: Papaya, Carica papaya.
• Review literature on Carica papaya, papain, and leaf and seed constituents.