Phytochemicals of Alpinia zerumbet: A Review

Alpinia zerumbet (Pers.) B.L.Burtt & R.M.Sm is a perennial plant of the Zingiberaceae family widely distributed in the subtropical and tropical areas of South America, Oceania, and Asia. Multiple plant parts of A. zerumbet have been traditionally used as medicinal sources, each with different clinical uses. These variations may arise from differences among the chemical components and/or accumulations of the active compounds in each part. Therefore, this review summarizes previous studies on the phytochemicals in A. zerumbet and reveals the similarities and differences among the chemical constituents of its multiple medicinal parts, including the leaves, rhizomes, fruits, seeds, and flowers. The results contribute to the scientific validation of the traditional understanding that A. zerumbet possesses different medicinal properties in each plant part. In addition, this review provides directions for further studies on the phytochemicals of this plant.

In the endemic regions of A. zerumbet, various parts of the plant have been used for various purposes.The leaves, rhizomes, fruits, seeds, and flowers of A. zerumbet have been traditionally used for medicinal purposes.In Brazil, a decoction of the leaves is believed to exhibit an anti-hemorrhoidal activity [14].Infusions, decoctions, and teas made from A. zerumbet leaves have been consumed as anti-hypertensives and diuretics [15][16][17].Especially in Marajó (Brazil), the leaves have been used as remedies for colds and influenza and are added to tea and bathwater [5].According to traditional Chinese folklore, the rhizomes of A. zerumbet can effectively treat trauma and peptic ulcers [18].The rhizomes are also used as a preservative or flavoring condiment in alcoholic beverages [19], and the seeds are a popular aromatic stomachic [18,20].The Miao people in Guizhou Province (China) have used the mature fruits (pericarps, placenta, and seeds) as cardiovascular disease treatments [7,21,22].In India, the rhizomes have been applied to sufferers of catarrhal and rheumatism affections [23].In Okinawa (Japan), the leaves are used in the traditional muchi cuisine (rice cake wrapped in A. zerumbet leaves), which is thought to protect against the common cold [24][25][26].The leaves are also sold as herbal teas [24,27], and their essential oils are used in cosmetics, perfumes, insect repellents, and deodorants [4,24].The seeds are employed as an aromatic stomachic [20,28] and were sold as Amomum seeds native to Japan in the first half of the twentieth century [29].In Martinique of the French West Indies, decoctions of A. zerumbet flowers have been used as a bronchitis treatment [12].Taiwanese indigenous peoples such as the Paiwan, Rukai, and Puyuma use the leaves in abay cuisine (leaf-covered rice with meat) [30].The flowers are incorporated into culinary preparations.The seeds are used as medicinal ingredients [30].In Vietnam, fever, abdominal pain, bloating, indigestion, and diarrhea are treated with a concoction obtained from boiled leaves, rhizomes, flowers, and seeds of the plant [13].
The number of studies on A. zerumbet has increased in recent times, revealing various bioactivities and pharmacological activities of the extracts and essential oils prepared from multiple medicinal parts of the plant (Table 1).These differences possibly arise from differences among the chemical components and/or the accumulation of active compounds in the individual medicinal parts.Therefore, by comprehensively clarifying the similarities and differences among the chemical constituents of the medicinal parts of A. zerumbet, we can better understand their different pharmacological activities and assess their clinical efficacies.This review summarizes the previous studies on the phytochemicals in A. zerumbet and clarifies the similarities and differences among the chemical constituents in multiple medicinal parts (leaves, rhizomes, fruits, seeds, and flowers) of the plant.The results contribute to the scientific validation of the traditional understanding that A. zerumbet possesses different medicinal properties in each part of the plant.Moreover, it provides researchers with a summary of the previous studies and directions for further studies.
Several studies are available on the chemical composition of essential oils extracted from A. zerumbet leaves collected in Brazil and Japan (Table 3).α-Thujene and α-terpinene are found in most of the essential oils in A. zerumbet leaves collected from Brazil, whereas camphene, camphor, (E)-methyl cinnamate, and α-humulene are found in most of those from Japan.
According to Victório et al. [125], the compositions of leaf and flower oils from A. zerumbet are very similar and differentiated mainly by their terpinen-4-ol concentrations (19.3% in leaf oil and 42.3% in flower oil).
Prudent et al. [14] compared the essential oils in the leaves, rhizomes, stems, and flowers of A. zerumbet collected from Martinique.Terpinen-4-ol was the major constituent in all parts, present at 29.8% in the leaves, 47.3% in the roots, 23.7% in the flowers, and 9.6% in the stems.
Hou et al. [87] identified 24 sesquiterpenes and 15 monoterpenes in the petroleum ether extract of the fruits.
In 2020, we clarified the chemical constituents in methanol extracts of A. zerumbet leaves, placenta, pericarps, and seeds using LC-MS [59].Compounds 1, 2, and 5-8 were detected in the leaf, placenta, and pericarp extracts but were absent in the seed extracts [59].Chompoo et al. [95] identified four steroids in the leaves, two steroids in the rhizomes and seeds, eight steroids in the pericarps, three steroids in the flowers, and five steroids in the stems of A. zerumbet.Another GC-MS analysis by Elzaawely et al. [70,96,139] revealed the presence of phenolic compounds in the ethyl acetate extracts of leaves, rhizomes, flower, and seeds.

Conclusions
A. zerumbet (Pers.)B.L.Burtt & R.M.Sm is a perennial plant widely distributed in South America, Oceania, and Asia.The medicinal properties of its leaves, rhizomes, fruits, seeds, and flowers are exploited in different clinical uses.The leaves of A. zerumbet have been consumed as antihypertensives and diuretics.The leaves are also believed to exhibit an anti-hemorrhoidal activity and to protect against the common cold.The rhizomes of A. zerumbet have been used to treat trauma, peptic ulcers, catarrh, and rheumatism.The seeds and fruits of A. zerumbet are traditionally used as an aromatic stomachic and cardiovascular disease treatment, respectively.A. zerumbet flowers have been used as a bronchitis treatment.
This review reveals that more than 100 compounds, including kavalactones, chalcones, flavonoids, terpenoids, diarylheptanoids, and neolignans, have been isolated from the leaves, rhizomes, fruits, pericarps, seeds, and flowers of this plant.This review also summarizes the chemical components of the organic solvent extracts and essential oils obtained from the various medicinal parts of A. zerumbet.The major components known at present are identified as the essential oil constituents, kavalactones, and flavonoids in the leaves; the essential oil constituents, kavalactones, flavonoids, and diterpenoids in the rhizomes; the essential oil constituents, kavalactones, and diterpenoids in the fruits (placenta, pericarps, and seeds); the essential oil constituents and diterpenoids in the seeds; and the essential oil constituents in the flowers.Most of the essential oils prepared from the leaves, rhizomes, and flowers of A. zerumbet are dominated by 1,8-cineole and terpinen-4-ol.No volatile components were found to uniquely accumulate in each medicinal part of the plant.These results contribute to the scientific validation of the traditional understanding that A. zerumbet possesses different medicinal properties in each plant part.
Although the chemical constituents of A. zerumbet have been extensively researched, phytochemical investigations have primarily focused on the leaves, rhizomes, and flowers of this plant; the fruit parts (pericarps, placenta, and seeds) have been comparatively limited.In addition, secondary metabolites such as chalcones, diarylheptanoids, and neolignans have been isolated from shell ginger but have not been quantitatively analyzed.Therefore, phytochemical investigation of A. zerumbet, especially of its fruit parts (pericarps, placenta, and seeds), and comparative quantitative investigations of the phytochemicals in the multiple medicinal parts (leaves, rhizomes, fruits, seeds, and flowers) would be valuable.

Table 1 .
Bioactivities of the extracts and essential oils of multiple medicinal parts of A. zerumbet.

Table 1 .
Cont.Hexane extract cals in the multiple medicinal parts of A. zerumbet which is written in English appears to be lacking.

Table 2 .
Compounds isolated from the multiple medicinal parts of A. zerumbet.

Table 3 .
Composition of the essential oils prepared from the leaves of A. zerumbet.

Table 4 .
Composition of the essential oils prepared from the leaves, rhizomes, fruits, seeds, and flowers of A. zerumbet.

Table 5 .
Contents of major kavalactones in multiple medicinal parts of A. zerumbet.