Ginger (Zingiber officinale) has been one of the best-known species since ancient times and is widely used in China and India. Although the wild species has not been found, it is believed to have originated from Malaysia, India, Sri Lanka, and Indonesia.
Zingiber officinale is an erect plant whose annual stalk is covered by an imbricated membranous sheath. It reaches a variable height between 0.60 and 1.50 m and grows on a thick, short rhizome.
Scaly leaves and bears cylindrical adventitious roots at the bottom part cover the rhizome. The rhizome has several horizontal ramifications bearing palmate fleshy tubers, eventually becoming fibrous. This plant’s aerial branches are annually renewed. Tall stalks (1.50 m) serve assimilation, and short ones (20 cm) serve reproduction.
Fresh or dried, previously peeled rhizomes of the Ginger species Zingiber officinale Roscoe are used.Ginger is grown mainly in tropical and subtropical areas with high temperatures and humidity. It is harvested when the aerial parts turn yellow and dry up, just after flowering, 8-10 months after sowing, and before the rhizomes become fibrous and hard.
Traditional Uses
Its beneficial properties have been appreciated for centuries and mentioned by the Chinese philosopher Confucius (551-479 BC), Dioscorides, and the Koran. The rhizome, which has been used dried as a spice or as a pickle for thousands of years in China, was most wanted in Europe during the Middle Ages. In oriental countries, it is considered an essential part of the daily diet to prevent illness and boost digestion.
Ginger has traditionally been used externally to treat osteoarticular inflammation, myalgia, muscle spasms, neuralgia, and odontalgia.
Chemistry
The most important compounds responsible for Ginger’s therapeutic activity are grouped into non-volatile and volatile compounds.
Non-volatile compounds
The non-volatile fraction consists of an oleoresin (4.0-7.5%). When this fraction is extracted with dissolvent, pungent elements, non-pungent elements, and an essential oil fraction are obtained.
Those elements are responsible for Ginger´s spicy flavor and partly responsible for its numerous beneficial actions have been identified as 1-(3’-methoxy-4’-hydroxyphenyl)-5-hydroxyalkan-3-ones, also known as the Gingerols group, which bear a lateral chain of variable length. In relation to these chains, the isolated and identified Gingerols have been named [3]-, [4]-, [5]-, [6]-, [8]- and [10]-Gingerol.More pungent but present in lower concentrations are the shogaols (phenylalkanones), products coming from dehydration of Gingerol, whose concentration increases during the drying process and the storing.
Other pungent elements, though present in lower proportion, are gingediols, gingediacetates, Gingerdione, and Gingerenones.
Volatile compounds
The composition of the volatile fraction consists mainly of the sesquiterpene derivatives (>50%), responsible for the aroma, whose concentration seems to remain constant. Such compounds include (-)-zingiberene (20-30%), (+)-ar-curcumene (6-19%), (-)-β-sesquiphelandrene (7-12%), and β-bisabolene (5-12%).The monoterpene derivatives are also a part of this essential oil, though in lower proportion. Among the ones, characteristic of Ginger, that have been isolated, we can mention α-pinene, bornyl acetate, borneol, camphene, p-cymene, cineol, citral, cumene, β-elemene, farnesene, β-phelandrene, geraniol, limonene, linalol, myrcene, β-pinene and sabinene.