Malaysian Herbal Monograph

Karas Leaves

Aquilaria malaccensis Lamk.


Figure 1 : A. malaccensis. (a) Whole plant; (b) leaves; (c) flowers; (d) fruit.  (Photos courtesy of FRIM, 2013)


Karas leaves consist of dried leaves of Aquilaria malaccensis Lamk. (Thymelaeceae).


Aquilaria agallocha Roxb., Agallochum malaccense (Lamk) Kuntze, Aquilariella malaccensis (Lamk) v. Tieghem [ 1 ].


Agar wood, malayan aloes-wood, malayan eaglewood (English); karas, gaharu, tengkaras (Malay); akil kattai (Tamil) [ 1 , 2 ].


ColourGreenish brown (powder)
TasteVery bitter


Plant Morphology

A. malaccensis is a tree, up to 20(–40) m tall; bark smooth, whitish. Leaves simple, alternate; petiole 4–6 mm long; blade elliptical-oblong to oblong-lanceolate, 7.5–12 cm x 2.5–5.5 cm, glabrous, sometimes pubescent and glabrescent beneath, shiny on both surfaces, base acute, attenuate or obtuse, apex acuminate, veins in 12–16 pairs, rather irregular, often branched, elevated and distinct beneath, curving upward to the margin, plane or obscure above. Inflorescence terminal, axillary or supra-axillary, sometimes internodal umbel, usually branched into 2–3 umbels, each with about 10 flowers; peduncle 5–15 mm long; pedicel slender, 3–6 mm long. Flowers usually 5-merous, campanulate, 5–6 mm long, green or dirty-yellow, scattered puberulous outside; floral tube nearly glabrous inside, distinctly 10-ribbed, persistent in fruit; calyx lobes 5, ovate-oblong, 2–3 mm long, almost as long as the tube, densely puberulous within; petaloid appendages 10, inserted at the throat of the tube, oblong or slightly ovate-oblong, about 1 mm long, slightly incurved, densely pilose; stamens 10, free, emerging from the throat of the tube, filamentous, 1.2–2 mm long, episepalous ones longer than the others; anthers linear, obtuse; pistil included; ovary ovoid, 1–1.5 mm long, 2-celled, densely pubescent; style obscure, stigma capitate. Fruit a loculicidal capsule, obovoid or obovoid-cylindrical, 3–4 cm x 2.5 cm, usually compressed, pubescent, glabrescent, base cuneate, apex rounded; pericarp woody. Seed ovoid, 10 mm x 6 mm including a beak 4 mm long, densely red-haired, bearing from the base a twisted, tail-like, pubescent appendage as long as the seed; seedling with epigeal germination [ 1 , 3 ].


Powdered material consists of abundant epidermis cells with straight to wavy anticlinal walled; also attached with stomata. Fragments of vessels with simple pitted, spiral and scalariform vessels with dark brown contents. Calcium oxalate crystals in prismatic and solitary form; sometimes attached with vessels and fibers [ 2 ].

Figure 2 : Microscopic characters of A. malaccensis leaves powder. (a-c) Epidermis cells (magnification 20x); (d-e) epidermis cells attached with stomata; (f-g) scalariform vessel cells (magnification 20x); (h-i) prismatic and solitary crystals [C]; spiral vessel cell and fibers (magnification 20x); (j) prismatic and solitary crystals [C] under polarizing filter (magnification 20x). [Scale bars: a-c, e-j = 20 µm; d = 100 µm]

Colour Tests 

Observed colour of solution after treatment with various reagents:

H2SO4 (conc.)Brown
NaOH (5%)Yellow

Thin Layer Chromatography (TLC)

Figure 3 : TLC profiles of mangiferin (S) and methanol extracts of A. malaccensis dried leaves powder (L1) observed under (a) UV at 254 nm before spray, (b) daylight after spray and (c) UV 366 nm after spray.

Test Solutions Weigh about 0.5 g of A. malaccensis dried leaves powder in a 50 mL screwed cap bottle and add 5 mL of methanol. Ultrasonicate the mixture for 15 min. Cool the mixture at room temperature and filter the solution with filter 0.45 µm into a vial. Use the filtrate as test solution.
Standard solution Dissolve mangiferin (CAS no.: 4773-96-0) in methanol to produce a solution containing 1 mg/mL.
Stationary Phase HPTLC glass silica gel 60 F254, 20 x 10 cm
Mobile phase Ethyl acetate : formic acid : acetic acid : water (100 : 11 : 11 : 25), 20 mL (v/v/v/v)
  1. Mangiferin standard solution (S); 4 µL, as a band.
  2. Methanol extract of A. malaccensis dried leaves powder (L1); 4 µL, as a band.
Development distance 8 cm, automatic developing chamber 2 (ADC2)
Drying Air drying
  1. Visible light.
  2. UV 254 nm.
  3. UV 366 nm, before and after spray with 10% sulphuric acid solution spray, then heat at 105°C for 3 min.

High Performance Liquid Chromatography (HPLC)

Test solution Weigh 0.5 g of A. malaccensis dried powder in glass vial with screw cap. Add 5 mL of methanol and ultrasonicate for 15 min.  Filter through 0.45 µm syringe filter and use the filtrate for HPLC analysis.
Standard solution Dissolve mangiferin (CAS no.: 4773-96-0) in methanol to produce a solution containing 1 mg/mL.
Chromatographic system

Detector: UV 254 nm

Column: C18 (5 µm, 4.6 mm i.d. x 250 mm) (preferably Luna C18, Phenomenex)

Column oven temperature: Ambient

Flow rate: 1.0 mL/min

Injection volume: 1 µL (test solution), 5 µl (standard solution)

Mobile Phase (gradient mode)

Run Time


A – 0.1% aqueous formic acid (%)

B – Acetonitrile (%)

C – Methanol (%)

























System suitability requirement

Perform at least five replicate injections of the standard solutions (1 mg/mL). The requirements of the system suitability parameters are as follow:

  1. Symmetry factor (As) is not more than 1.5.
  2. Percentage of relative standard deviation (RSD) of the retention time (tr) for mangiferin standard is not more than 2.0%.
Acceptance criteria
  1. Retention time (tr) of mangiferin in the test solution is similar to the tr of mangiferin in the standard solution.
  2. The ultraviolet (UV) spectrum of mangiferin in the test solution is similar to the UV spectrum of the standard solution (optional supportive data).
fig4 a


fig4 b


Figure 4 : HPLC profile of mangiferin standard solution; (a) full and (b) zoom chromatogram at tr = 15.321 min.

fig5 a


fig5 b


Figure 5 : HPLC profiles of methanol extracts of A. malaccensis dried leaves powder (a) full and (b) zoom chromatograms at tr = 15.358 min. 


Figure 6 : UV spectrum of mangiferin standard solution (1.0 mg/mL) and methanol extracts of A. malaccensis dried leaves powder.


Foreign Matter
Not more than 2%
Ash Contents
Total ash Not more than 6%
Acid-insoluble ash Not more than 1%
Loss on Drying
Not more than 11%
Extractive Values
Water-soluble extracts
Hot method Not less than 22%
Cold method Not less than 16%
Ethanol-soluble extracts
Hot method Not less than 19%
Cold method Not less than 12%


Heavy Metals
Arsenic Not more than 5.0 mg/kg
Mercury Not more than 0.5 mg/kg
Lead Not more than 10.0 mg/kg
Cadmium Not more than 0.3 mg/kg
Microbial Limits
Total bacterial count Not more than 105 cfu/g
Total yeast and mould count Not more than 104 cfu/g
Bile-tolerant gram negative Not more than 104 cfu/g
Specific Pathogens
Salmonella spp. Absent in 25 g
Escherichia coli Absent in 1 g
Staphylococcus aureus Absent in 1 g
Pseudomonas aeruginosa Absent in 1 g


Methanolic extract of A. malaccensis leaves has been found to contain fatty acids (e.g. n-hexadecanoic acid and 9,12,15-octadecatrienoic acid (z,z,z)-, fatty alcohols (e.g. 3,7,11,15-tetramethyl-2-hexadecen-1-ol (phytol) and 1-tetradecanol), polyol (e.g. glycerine), pyrone (e.g. 2,3-dihydro-3,5-dihydroxy-6-methyl-4H-pyran-4-one), quinone (e.g. 6-ethyl-5-hydroxy-2,3n,7-trimethoxynaphthoquinone), triterpene (e.g. squalene) and others (2-propanone,1,2,dihydroxy, dodecyl acrylate and octaethylene glycol monodecyl ether) [ 4 ].

The methanolic extract was also found to contain xanthone (e.g. mangiferin) [ 5 ].


Uses described in folk medicine, not supported by experimental or clinical data

Information and data have not been established.

Biological and pharmacological activities supported by experimental data

Antioxidant activity

Crude extracts of A. malaccensis leaves (0.156 to 10.000 μg/mL) showed 2,2-diphenyl-1-picrylhydrazyl (DPPH) free radical scavenging activity with IC50 values of 800 µg/mL,  160 µg/mL,  140 µg/mL and  30 µg/mL for the hexane, dichloromethane, ethyl acetate and methanol extract, respectively as compared to quercetin (IC50 = 3.33 µg/mL) [ 6 ].

Hepatoprotective activity

Ethanol (95%) extract of A. malaccensis leaves (200 and 400 mg/kg) administered orally to rats (150 to 200 g) for a duration of ten days after induction of liver toxicity using carbon tetrachloride (CCl4) significantly (p < 0.05) decreased the level of aspartate transaminase (AST: 242.00 ± 4.86 U/L), alanine transaminase (ALT: 153.17 ± 3.77 U/L) and alkaline phosphates (ALP: 88.90 ± 4.98 U/L) compared to the carbon tetrachloride-treated control group (AST: 300.30 ± 5.78 U/L, ALT: 252.0 ± 5.84 U/L, ALP: 111.5 ± 4.22 U/L) [ 7 ].

Antibacterial activity

Aqueous extract of A. malaccensis leaves (50 mg/mL) showed antibacterial effect against Shigella flexneri with inhibition zone 18 mm compared to gentamicin (10 mm) using agar diffusion assay [ 8 ].

Methanol extract of A. malaccensis leaves (50 mg/mL) showed antibacterial effect to Bacillus subtilis with inhibition zone 19 mm compared to gentamicin (10 mm) using agar diffusion assay [ 8 ].

Clinical studies

Information and data have not been established.


Preclinical studies (Toxicology studies)

Acute toxicity

Oral single dose acute toxicity study using aqueous extract of A. malaccensis leaves on female Sprague Dawley rats (aged between 8 and 12 weeks old) showed no toxic effect on the parameters observed which includes behaviors, body weight, food and water intakes. All rats were observed for 14 days prior to necropsy. No death was found throughout the study period. No-observed-adverse effect level (NOAEL) is more than 2,000 mg/kg body weight [ 9 ].

Others (Adverse reaction, contraindication, side effect, warning, precaution)

Information and data have not been established.


Information and data have not been established.


Store below 30°C. Protect from light and moisture.


  1. Chung RCK and Purwaningsih. Aquilaria malaccensis Lamk. In: Oyen LPA and Nguyen XD (Editors). Plant Resources of South-East Asia No. 19: Essential-oil plants. Backhuys Publisher, Leiden, The Netherlands. 1999. pp. 64–67.
  2. Government of India Ministry of Health and Family Welfare Department of Ayush. Agaru (Ht. Wd.). Part 1. Volume 4. 2013. pp. 4-5.
  3. Wang Y, Nevling LI, Gilbert MG. Flora of China: Thymelaeaceae.  Vol. (13). Science Press, Beijing and Missouri Botanical Garden Press, St. Louis. 2008. pp. 214.
  4. Khalil AS, Rahim AA, Taha KK, Abdallah KB. (2013) Characterization of methanolic extracts of Agarwood leaves. Journal of Applied and Industrial Sciences 2013;1(3):78–88.
  5. Tan HP, Ling SK, Tan AL, Mohd Faisal IS, Siti Kamariah MH, Nuraini AM. Phytochemical study on the leaves of Aquilaria malaccensis Lam. Paper presented at 17th Malaysian Chemical Congress (17MCC); Kuala Lumpur; 2012 Oct 15-7.
  6. Huda AWN, Munira MAS, Fitrya SD and Salmah M. Antioxidant activity of Aquilaria malaccensis (Thymelaeaceae) leaves. Pharmacognosy Research 2009;1(5):270–273.
  7. Vakati K, Rahman H, Eswaraiah MC, Dutta AM. Evaluation of hepatoprotective activity of ethanolic extract of Aquilaria agallocha leaves (EEAA) against CCl4 induced hepatic damage in rat. Scholars Journal of Applied Medical Sciences 2003;1(1):9–12.
  8. Dash M, Patra JK, Panda PP. Phytochemical and antimicrobial screening of extracts of Aquilaria agallocha Roxb. African Journal of Biotechnology 2008;7:3531–3534.
  9. Teh BP, Hamzah NF, Norazila Z, Norliyana MY, Wan Abdul Hakim WL. Acute oral toxicity study of selected Malaysian medicinal herbs on Sprague Dawley rats. Institute for Medical Research, Ministry of Health; 2014. Report no.: HMRC 11-045/01/AM/L/B.