Agarwood (or just Agar) is a dark resinous heartwood that forms in Aquilaria trees (large evergreens native to southeast Asia) when they become infected with a type of mold. Prior to infection, the heartwood is relatively light and pale coloured, however as the infection progresses, the tree produces a dark aromatic resin in response to the attack, which results in a very dense, dark, resin embedded heartwood. The resin embedded wood is commonly called gaharu, jinko, aloeswood, agarwood, or oud (not to be confused with ‘Bakhoor’) and is valued in many cultures for its distinctive fragrance, and thus is used for incense and perfumes.
One of the reasons for the relative rarity and high cost of agarwood is the depletion of the wild resource. Since 1995 Aquilaria malaccensis, the primary source, has been listed in Appendix II (potentially threatened species) by the Convention on International Trade in Endangered Species of Wild Fauna and Flora. In 2004 all Aquilaria species were listed in Appendix II; however, a number of countries have outstanding reservations regarding that listing.
History of Agarwood
The odour of agarwood is complex and pleasing, with few or no similar natural analogues. As a result, agarwood and its essential oil gained great cultural and religious significance in ancient civilizations around the world, being mentioned throughout the oldest written texts – the Sanskrit Vedas from India.
Starting in 1580 after Nguyen Hoang took control over the central provinces of modern Vietnam, he encouraged trade with other countries, specifically China and Japan. Agarwood was exported in three varieties: Calambac (kỳ nam in Vietnamese), trầm hương (very similar but slightly harder and slightly more abundant), and agarwood proper. A pound of Calambac bought in Hoi An for 15 taels could be sold in Nagasaki for 600 taels. The Nguyen Lords soon established a Royal Monopoly over the sale of Calambac. This monopoly helped fund the Nguyen state finances during the early years of the Nguyen rule.
Xuanzang’s travelouges and the Harshacharita, written in 7th century A.D. in Northern India mentions use of Agarwood products such as ‘Xasipat’ (writing-material) and ‘aloe-oil’ in ancient Assam (Kamarupa). The tradition of making writing-materials from its bark still exist in Assam.
Agarwood is known under many names in different cultures:
- In Hindi (India), it is known as “agar”, which is originally Sanskrit based.
- It is known as Chén-xīang (沉香) in Chinese, “trầm hương” in Vietnamese, and Jin-koh (沈香) in Japanese; all meaning “sinking incense” and alluding to its high density.
- Both agarwood and its resin distillate/extracts are known as Oud (عود) in Arabic (literally wood) and used to describe agarwood in nations and areas of Islamic faith. Western perfumers may also use agarwood essential oil under the name “oud” or “oude”.
- In Europe it was referred to as Lignum aquila (eagle-wood) or Agilawood, because of the similarity in sound of agila to gaharu.
- Another name is Lignum aloes or Aloeswood. This is potentially confusing, since a genus Aloe exists (unrelated), which has medicinal uses. However, the Aloes of the Old Testament (Num. 24:6; Ps. 45:8; Prov. 7:17; and Cant. 4:14) and of the Hebrew Bible (ahalim in Hebrew) are believed to be agarwood from Aquilaria malaccensis.
- In Tibetan it is known as a-ga-ru. There are several varieties used in Tibetan Medicine: unique eaglewood: ar-ba-zhig ; yellow eaglewood: a-ga-ru ser-po, white eaglewood: ar-skya, and black eaglewood: ar-nag.
- In Assamese it is called as “ogoru”.
- The Indonesian and Malay name is “gaharu”.
- In New Guinea it is called “ghara”.
- In Thai language it is known as “Mai Kritsana” (ไม้กฤษณา).
- In Laos it is known as “Mai Ketsana”.
Formation of Agarwood
There are fifteen species in of the Aquilaria genus and eight are known to produce agarwood. In theory agarwood can be produced from all members; however, until recently it was primarily produced from A. malaccensis. A. agallocha, and A. secundaria are synonyms for A. malaccensis. A. crassna and A. sinensis are the other two members of the genus that are usually harvested.
Formation of agarwood occurs in the trunk and roots of trees that have been infected by a parasitc ascomycetous mold, Phaeoacremonium parasitica, a dematiaceous (dark-walled) fungus. As a response, the tree produces a resin high in volatile organic compounds that aids in suppressing or retarding the fungal growth. While the unaffected wood of the tree is relatively light in colour, the resin dramatically increases the mass and density of the affected wood, changing its colour from a pale beige to dark brown or black. In natural forest only about 7% of the trees are infected by the fungus. A common method in artificial forestry is to inoculate all the trees with the fungus.
High quality resin comes from a tree’s natural immune response to a fungal attack. It is commonly known as agarwood #1 (first quality). An inferior resin is created using forced methods where aquilaria trees are deliberately wounded, leaving them more susceptible to a fungal attack. This is commonly called agarwood #2.
Odor profile of Agarwood
A natural perfume oil obtained by CO2 extraction from agarwood retains the odor of “true” agarwood: a cepes (mushroom) and carrot seed accord, which can be roughly approximated by combining ambergris, jasmine, earth and wood notes. Lightly infected wood, sometimes cultivated, produces an (allegedly) inferior oil with a vetiver, sandalwood, and patchouli character.
Characteristics of Agarwood
The cheapest Aoud oil distilled from agarwood can cost as little as $20 per kilogram, while the finest Oud oils distilled from agarwood can cost as much as $7,000 per kilogram.Yves Saint Laurent uses Agarwood in perfume products, though Aloeswood/Oud oil is not commonly known in the Western world.
Aquilaria species that produce Agarwood
See: Ng, L.T., Chang Y.S. and Kadir, A.A. (1997) “A review on agar (gaharu) producing Aquilaria species” Journal of Tropical Forest Products 2(2): pp. 272-285.
- Aquilaria apiculina, found in Philippines
- Aquilaria baillonil, found in Thailand and Cambodia
- Aquilaria baneonsis, found in Vietnam
- Aquilaria beccarain, found in Indonesia
- Aquilaria brachyantha, found in Malaysia
- Aquilaria crassna found in Malaysia, Thailand, and Cambodia
- Aquilaria cumingiana, found in Indonesia and Malaysia
- Aquilaria filaria, found in China
- Aquilaria grandiflora, found in China
- Aquilaria hilata, found in Indonesia and Malaysia
- Aquilaria khasiana, found in India
- Aquilaria malaccensis, found in Malaysia, Thailand, and India
- Aquilaria microcapa, found in Indonesia and Malaysia
- Aquilaria rostrata, found in Malaysia
- Aquilaria sinensis, found in China
- Aquilaria subintegra, found in Thailand
Conservation of Agarwood-producing Species
Overharvesting and habitat loss threatens some populations of agarwood-producing species. Concern over the impact of the global demand for agarwood has thus led to the inclusion of the main taxa on CITES Appendix II, which requires that international trade in agarwood is subject to controls designed to ensure that harvest and exports are not to the detriment of the survival of the species in the wild.
In addition, agarwood plantations have been established in a number of countries. The success of these plantation depends on the stimulation of agarwood production in the trees. Numerous inoculation techniques have been developed, with varying degrees of success.