Distribution and Importance of the Plant
Rubiaceous plants of the genus Genipa grow throughout tropical America, and Genipa americana L. (synonym G. caruto H.B. & K.) (Fig. 1 A) is native to the wet or moist areas of Cuba, Hispaniola, Puerto Rico, the Virgin Islands, and from Guadeloupe of Trinidad; also from southern Mexico to Panama, and from Colombia and Venezuela to Peru, Brazil, Bolivia, Paraguay, and Argentina. The fruit (), which is edible and popular as a source for beverages, has many colloquial names: marmalade box in the former British West Indies, genipa, jagua or caruto in Puerto Rico and several other Spanish-speaking countries; genipapo, jenipapo or jenipa in parts of Columbia and Brazil; chipara, chibara or guanapay among Colombian Indians; carucarutoto, caruto rebalsero, or guaricha in Venezuela, tapoeripa in Surinam, lana in Guyana; bi, bicito or totumillo in Bolivia; huitoc, vito, vitu or palo Colorado in Peru; maluco in Mexico; crayo, irayol de montana, guaitil or tapaculo in Costa Rica; irayol, tambor or tine-duentes in El Salvador; and guayatil Colorado or jagua blanca in Panama (). This tree is strictly tropical and grows well in a humid atmosphere and deep loamy soil. The erect trunk of the tree with spreading branches is over 30 m in height. The leaves, deciduous, especially at the rapid lowering of ambient temperatures, are opposite but mostly clustered at the tip of the branch, oblong, 10-30 cm in length, and have a prominent midrib. The tubular five-petaled flowers are yellowish, and ca. 4 cm in width. The elliptic fruit, ca. 10 cm in length, and bearing a short hollow tube at the apex, contains white flesh, which turns yellow to bluish-purple and finally to jet-black on exposure to the air (). It was reported that the natives bathed their limbs and sometimes the whole body, when tired, in a clear juice obtained from the fruits, which turned everything it touched as black as fine and polished jet (Oviedo 18th century).
The tree first fruited in the Philippines in 1913 and is occasionally planted there (). It was introduced into Java in 1913 ().
Although the fruit has long been used to make drinks () and dyestuffs (), the discovery of various medicinal properties have made the Genipa plant an important medicinal resource. Genipin () was isolated from the ripe fruit () and the structure was elucidated (). Two cyclopentanoid monoterpenes, genipic acid () and genipinic acid (), were isolated from Puerto Rican Genipa americana fruit (). Genipin (), however, was not obtained from that source (). Later, geniposidic acid () was isolated as a powder from the leaves of Genipa americana collected in Darien, Panama (). Gardenia jasminoides Ellis, a related rubiaceous plant growing throughout subtropical to temperate East Asia from Vietnam to the southern part of Japan () also produces geniposidic acid (), geniposide (), a glucoside of genipin (), and genipin gentiobioside along with gardenoside (). Later, tarennoside (), the main iridoid glucoside of Okinawan Tarenna gracilipes () Ohwi () together with 2, 3, and 4 were obtained from the cultured cells of Gardenia jasminoides (). Through administration of the isotope-labeled putative precursors to the Gardenia jasminoides cell cultures, the biosynthetic sequence 1 -> 2 -> 3 -> 4, started from mevalonic acid, has been established (). Genipin () has purgative () and choleretic activities (). This compound, as well as geniposide (), inhibited the germination of Gardenia jasminoides seeds and watercress (Nasturtium officinale R. Br.) seeds and the growth of Chinese cabbage (Brassica rapa L. var. pervidis Bailey) Shimomura et al.. When genipin () was reacted with glycine, genipocyanin G1, an azaphilone iridoid dimer of a 1:1 adduct between glycine and genipin () was formed (). Reaction of genipin () with cytochrome C (horse heart) gave higher-molecular weight oligomers formed by the inter-molecular cross-linkage of proteins mediated by the iridoid (). This finding may open way for the development of a new type of cross-linking reagent. Recently, genipin () was found to have a remarkable tumor-promotion inhibitory activity on Epstein-Barr virus activation. Among the above described four iridoid glucosides, tarennoside () is the most active, but the activity decreases with the progress of the metabolism. Although the activity of geniposide () is lower than that of geniposidic acid (), its aglycone genipin () is remarkably active (). This finding is compatible with the general observations that glycosylation participates in reducing the biological activity ().
Conventional Practices for Its Propagation and the Production of Iridoids
The propagation of Genipa americana plants has been attempted at several sites in tropical areas with a view to the exploitation of the fruit for liquor manufacture. Despite some successful cases, the trials of the introduction of this strictly tropical tree into other areas have often failed. Sometimes even well-growing trees have never bloomed. Stricter conditions are required for fruiting. The leguminous Erythrina glauca tree has an advantage in increasing the soil-nitrogen content in addition to the role as a shade tree in a cacao plantation, while the rubiaceous Genipa tree does not contribute to the direct increase in soil nitrogen ().
Genipin (), an iridoid, was reported as a constituent of Genipa americana fruit (). This compound, however, was not detected in the methanol extracts of Genipa americana fruits, collected at Bogor, Indonesia in October 1983 and at Rio de Janeiro, Brazil in July 1990. The fresh fruits were extracted with hot methanol immediately after being cut into slices. A conventional work-up of both methanol extracts gave geniposide () and geniposidic acid (), respectively, as colorless needles (). Dried fruit slices, colored bluish-purple, gave genipin (), as reported previously. A crystalline component isolated from the wood of Genipa americana was found to be D-mannitol ().
Genipin () itself has a potentially high demand in the world market, especially for choleretic and tumor inhibitory drugs. This compound (), also obtainable by the hydrolysis of Gardenia geniposide (), could be a starting material for the synthesis of biologically active cyclopentanoid substances such as prostaglandins () and triquinane sesquiterpenes (). Demand for the genipin-derived food dyestuffs could also be expected ().
Genipin (), the aglycone of geniposide () has been found to be an important material for the production of food dyestuffs, beverages, and medicines (). Genipa americana fruit was found to contain a considerable amount of geniposide (), which is also one of the main constituents of Gardenia jasminoides, commonly distributed in subtropical and temperate East Asia. Although the present supply is considered as meeting the current demand, the finding of a highly inhibitory activity in the fruit against tumor promotion will raise the demand with the advance of the development of advantageous biological activities. The success of raising rediflerentiated Genipa americana plants will contribute to the protection of tropical rain forests. Contrary to the conventional observations of reduced secondary metabolite productivity in the cell cultures, a combination of selection procedures has led to the establishment of high iridoid-producing Genipa cell lines. The selection procedures suggest a general way to improve the secondary metabolite production.
Selections from the book: “Medicinal and Aromatic Plants IV”, 1993.