Aquilaria malaccensis

Aquilaria malaccensis, commonly known as agarwood tree, gharu wood, or malacca eaglewood, is a tropical tree species belonging to the family Thymelaeaceae. It is best known as the principal source of agarwood, a highly valuable resinous wood used in perfumery, incense, and traditional medicine. Native to South and Southeast Asia, this species has been prized for centuries for its aromatic qualities and cultural significance, particularly in the Middle East and Asia. Due to overexploitation, Aquilaria malaccensis is now classified as critically endangered in many regions and is listed under CITES Appendix II to regulate its international trade.

Botanical Description

A. malaccensis is a medium to large evergreen tree, typically growing up to 30–40 metres in height and 60–80 centimetres in trunk diameter under natural conditions. The tree has a straight cylindrical bole, a smooth greyish bark that turns darker with age, and a dense canopy of alternate leaves.

• Leaves: Simple, lanceolate or oblong in shape, 5–12 cm long, dark green on the upper surface and pale beneath, with numerous fine lateral veins.
• Flowers: Small, greenish-yellow to white, and fragrant, arranged in clusters at the ends of twigs. Flowering usually occurs once a year, followed by fruiting.
• Fruits: Capsule-like, ovoid, 2.5–3 cm long, containing one or two seeds covered with fine hairs. When mature, the fruit splits open to release the seeds.

The tree grows well in humid tropical climates with well-drained soils, often found in lowland rainforests, hill slopes, and river valleys up to altitudes of about 1,000 metres. It thrives in regions receiving an annual rainfall of 1,800–3,500 mm and prefers slightly acidic soils rich in organic matter.

Distribution and Habitat

A. malaccensis is distributed across South and Southeast Asia, including India (particularly Assam and the North-Eastern states), Bangladesh, Bhutan, Myanmar, Thailand, Malaysia, Indonesia, and parts of Laos and Vietnam. The species name malaccensis derives from Malacca (now Melaka in Malaysia), one of the areas where it was first described.
In India, it is mainly found in the Assam Valley, Arunachal Pradesh, Meghalaya, Tripura, and Manipur. Natural populations are often found in mixed tropical evergreen forests but have declined drastically due to extensive harvesting for agarwood production and habitat loss.

Agarwood Formation and Resin Production

The economic and cultural importance of A. malaccensis lies in its ability to produce agarwood, a dark, resinous heartwood that forms as a pathological response to fungal infection or physical injury. When the tree is wounded or infected by certain fungi—particularly species of Fusarium, Aspergillus, or Penicillium—it secretes an aromatic resin as a defence mechanism. Over time, the resin-impregnated wood darkens and becomes highly fragrant.
Agarwood is valued for its complex aroma, which develops during slow oxidation and distillation processes. The resin content and quality vary depending on factors such as tree age, infection duration, and environmental conditions. Only a small fraction of A. malaccensis trees naturally produce agarwood, making it extremely rare and valuable.
Modern techniques, such as artificial inoculation using fungal cultures or chemical stimulation, have been developed to induce agarwood formation in cultivated trees, thereby reducing pressure on wild populations.

Economic and Cultural Importance

Agarwood derived from A. malaccensis is one of the most expensive natural products in the world. It is used in multiple industries, with its value ranging from hundreds to thousands of US dollars per kilogram, depending on purity and quality.

1. Perfumery and Incense:
   • The oil extracted from agarwood, known as oud or gaharu oil, is a premium ingredient in luxury perfumes, particularly in the Middle East and Japan.
   • Agarwood chips and powder are burned as incense in religious and ceremonial rituals in Buddhist, Hindu, Islamic, and Japanese traditions.
2. Traditional Medicine:
   • In Ayurvedic, Chinese, and Unani medicine, agarwood is used for treating respiratory disorders, digestive issues, and as a sedative.
   • It is believed to have antimicrobial, anti-inflammatory, and analgesic properties.
3. Religious and Cultural Uses:
   • Agarwood is mentioned in ancient scriptures such as the Vedas, Tripitaka, and Old Testament, signifying its long-standing spiritual importance.
   • It continues to be an essential offering material in temples and monasteries across Asia.

Conservation Status and Threats

Due to the high market demand for agarwood, Aquilaria malaccensis has suffered from unsustainable logging and illegal harvesting, leading to a drastic reduction in wild populations. The species is now considered vulnerable to critically endangered across its native range.
Key threats include:

• Overexploitation: Unregulated felling of trees in search of resinous wood.
• Habitat Loss: Deforestation for agriculture and development.
• Illegal Trade: Smuggling of agarwood and essential oils across borders.
• Low Natural Regeneration: Due to limited seed dispersal and selective harvesting of mature trees.

In recognition of its endangered status, A. malaccensis was listed in Appendix II of the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES) in 1995. This restricts its international trade unless accompanied by proper permits ensuring that exports do not threaten the species’ survival.
In India, it is protected under the Wildlife Protection Act, 1972, and its felling or export without government approval is prohibited.

Cultivation and Sustainable Management

To address declining natural populations, several countries have initiated plantation programmes and agroforestry systems for cultivating A. malaccensis. India, Malaysia, and Indonesia have established large-scale agarwood plantations to ensure sustainable production.
Important cultivation measures include:

• Selection of disease-resistant seedlings from high-quality genetic stock.
• Maintenance of proper spacing, soil conditions, and shade.
• Artificial inoculation using fungal strains to induce resin formation after 6–8 years of growth.
• Monitoring tree health and preventing pest or fungal damage that can affect yield quality.

Sustainable harvesting practices are encouraged through community forestry programmes and certified agarwood trade networks, promoting conservation while providing economic opportunities for local communities.

Chemical Composition and Fragrance Profile

The characteristic aroma of agarwood arises from complex sesquiterpenes and chromone derivatives, including agarol, agarospirol, jinkoh-eremol, and benzylacetone. These compounds produce a distinctive, rich, and warm scent with woody, balsamic, and slightly sweet undertones. The composition varies depending on the species, resin age, and distillation process.
Agarwood oil is obtained by steam or hydro-distillation of resinous wood chips. The resulting oil is graded based on purity, colour, and intensity of fragrance, with higher grades commanding premium prices in the international market.

Research and Modern Applications

Contemporary research focuses on the biotechnology of agarwood formation, chemical profiling, and conservation genetics of A. malaccensis. Advances in DNA barcoding have improved species identification, helping curb illegal trade. Studies on microbial interactions and environmental triggers aim to optimise resin production without depleting wild populations.
Beyond perfumery and medicine, agarwood oil is being explored for aromatherapy, cosmetics, and pharmaceutical formulations due to its potential therapeutic benefits such as stress relief, anti-oxidation, and antimicrobial activity