|Quassia amara from Koehler's Medicinal-Plants (1887)|
Quassia amara, also known as amargo, bitter-ash, bitter-wood, or hombre grande (spanish for big man) is a species in the genus Quassia, with some botanists treating it as the sole species in the genus. The genus was named by Carl Linnaeus who named it after the first botanist to describe it: the Surinamese freedman Graman Quassi. Q. amara is used as insecticide, in traditional medicine and as additive in the food industry.
Name, image, harvested organ
Quassia (genus) amara (species) is an attractive small evergreen shrub or tree from the tropics and belongs to the family Simaroubaceae. Q. amara was named after called Graman Quassi, and enslaved healer and botanist who showed Europeans the plant’s fever treating uses.
The name “amara” means "bitter" in Latin and describes its very bitter taste. Q. amara contents more than thirty phytochemicals with biological activities in its tissues including the very bitter compound quassin. Therefore, it is used as insecticide, in traditional medicine against lot of disease and as bitter tasting additive in the food industry. All plant parts are useful for medicinal properties and the bark extracts are mainly used as flavoring in drinks but also for insecticides.
Q. amara grows wild, but can be cultivated. Trunk wood, roots, bark, stems, leaves, flowers and seeds are harvested to gain extracts of the plant. For its beauty, quassia is also grown as ornamental plant.
Quassia amara is marketed and used interchangeably with another tree species Picrasma excelsa, sharing the common name of quassia (and many of Quassia amara's constituents and uses). P. excelsa is with up to 25 m in height much taller, and occurs farther north in the tropics of Jamaica, the Caribbean, the Lesser Antilles, and northern Venezuela than Quassia amara. Also in herbal medicine in the United States and Europe very little distinction is made between these two species of trees; they are used identically and just called quassia.
Quassia alatifolia, Q. officinalis, Q. amargo, Simaroube officinale
Amargo, Bitter ash, Bitterholz, Bitterwood, Bois amer, Bois de quassia, Crucete, Quassia, Cuassia, Cuachi, Fliegenholz, Guabo, Hombre grande, Jamaica bark, Kashshing, Marauba, Marupa, Palo muneco, Pau amarelo, Quassia amarga, Quassiawood, Ruda, Simaruba, Simarubabaum, Quassiaholz, Quassia de cayenne, Quassie, Quina, Simaba, Suriname wood
Morphology, life form and growth
A small, multistemmed and slow growing tree with a disorderly growth twiggy limbs. It is a shrub or rarely a small tree, reaching a height up to 6 metres. The pinnate with 3-5 leaflets, deeply veined, polished alternated dark green leaves are 15–25 cm long and distinctive for their broadly winged axis and reddish veins. Leaf rachis are winged. Terminal red-branched racemes of panicles, 10–30 cm long, produces narrow, vivid crimson flowers, 2.5-3.5 cm long, that decorate the tips of each little limb. The flower comprises 5 lanceolate petals, which remain mostly closed together forming a sharpening cylinder. The flowers are produced in a panicle 15–25 cm long, each flower 2.5-3.5 cm long, bright red on the outside, and white inside. They are generally open for two days during the flowering period and each inflorescence presents on to four open flowers at once. The flowers are fragile and sometimes fall from the rachis at the slightest touch. The fruits, five small eliptic, fleshy, purple black drupes, 0.8-1.5 cm long, replace the flower and turn red as they mature. Every fruit contains one small seedling. All parts of Q. amara contain the bitter Quassimarin.
Origin and regions of cultivation
Quassia amara is an understorey plant in neotropic rainforests and humid sites and mostly abundant in young forests. Therefore Q. amara is native in the tropicals of Southern America. More exactly in the Caribbean (Trinidad and Tobago), Central America (Costa Rica, Nicaragua, Panama), Northern South America (French Guiana, Guyana, Suriname, Venezuela, Brazil, Peru) and in Western South America (Colombia, Argentina). It is found in the Amazon Rainforest at altitudes ranging from sea level to 900 m. Q. amara is traditionally harvested in natural forests. There are reports of cultivation in other countries of Central and South America. It inhabits zones of high precipitation (1500–4500 mm per year), and may appear in dry lands or in riparian lands where there is a high humidity permanent. Q. amara is widely planted outside its native range.
Soil, climate and light requirements
Q. amara is suitable for medium (loamy) and heavy (clay) soils. It prefers rich soils, that are water retentive. The tree can adapt to different pH-values in soils. It is a frost sensitive plant. Its salt toleration and dry toleration is low. It is classified as a semi-sciophyte with high tolerance to shade conditions but with a requirement of direct exposure to sunlight in order to complete its life cycle, in particular due to its effect on ﬂower and fruit production. An increase in the light conditions increases ﬂower and fruit production although it does not inﬂuence seed fertility. Therefore, its natural regeneration appears to be limited by light and interspeciﬁc competition with upperstorey forest species.
Other identified components of bitterwood are: beta-carbolines, beta-sitostenone, beta-sitosterol, dehydroquassins, gallic acid, gentisic acid, hydroxyquassins, isoparain, isoparaines, isoquassins, malic acid, methylcanthins, methoxycanthins, methoxycantins, nigakilactone A, nor-neoquassin, parain, paraines[check spelling], quassialactol, quassimarin, quassinol, quassol and simalikalactone D.
Additive in food industry
The bitter principle found in the bark and wood is used as the basis of Angostura Bitters, which is used as a flavouring in longdrinks, soft drinks, digestive tonics and also in gin-based drinks. It can be used as a substitute for hops in beer manufacturing or can be added to baked goods.
The component Simalikalactone D was identified as an antimalarial. The preparation of a tea out of young leaves is used traditionally in French Guiana. Experiments showed a high inhibition of Plasmodium yoelii yoelii and Plasmodium falciparum.
Quassia amara is part of the family of the Simaroubaceae, which contains quassinoids. Those are secondary metabolites that have a large range of biological activities. The plant is known for the active principles that can be found in its bark. They have several different effects like increasing appetite, tonic, diuretic, febrifugal, anthelmintic and anti-leukemic. It also leads to more activity from the gall bladder and has an effect against liver congestion. At external use, they act efficacy against parasites like pinworms. It is also a tribal remedy used in South America against debility, liver problems, malaria, snakebite, and back spasms. The Quassia amara is sold in the form of ground-up chips that are used to produce tonic or tinctures. Those are made by soaking the bark in the water for a long time.
There are two varieties of Q. amara that can be used in medicine. It is the West Indian type and the South American variety. The West Indian is high, it can reach 30.5m, the South American is much smaller, with a heigh from 5.5m.
In 2011 Husein and Gulam Mohammed, found that Q. amara extract reduced the elevated fasting blood glucose in rats. It also shows that glucose tolerance is increased by the consumption of Q. amara. According to Ferreira and al. 2013, the wood powder of Q. amara shows an anti-hyperglycemic effect, similar to the one from metformin. It could be helpful as an alternative therapy to the existing drugs that cause adverse health effects.
Tea made with the leaves of the Q. amara, is used against malaria in the traditional medicine of French Guiana. The leaves hexane from Q. amara was found to have high suppressive activity, at a concentration from 100 mg/kg body weight in mouse. In 2006, a study found that Simalikalactone D should be responsible for the antimalarial activity. In 2009, a new quassinoid was discovered, the simalikalactone E. This molecule inhibited the growth of P. falciparum in vitro by 50%. The effect was mostly found in the gametocyte, which is the stage that is fundamental for the transmission to mosquitoes. The tea from Quassia amara has also an effect on the red blood cells counts, the packed cell count, the packed cell volume and hemoglobin concentration. It has an antianemic property.
Quassia amara is used in folk medicine from Costa Rica. Searchers from the University of Ibadan found a significant inhibition of the gastric ulceration induced by indomethacin. The amount of protection was between 77% and 85%. It also reduces the total gastric acidity. It was related to an increase in gastric barrier mucus and non-protein sulfhydryl groups.
Quassia amara is also used it this traditional Indian medicine, the Ayurvedic medicine to treat rheumatism, alcoholism, dandruff, stomach problems, and worms. It is also used in the homeopatic medicine.
Excessive use of this plant can cause vomiting. It is also to avoid to use in the long term, because it can lead to a weakness of the vision, going to total blindness. It should also be avoided during pregnancy and menstruation, because it may cause uterine colic. It has also shown to have negative effects on the fertility of rats, both male and females. It has been proven to reduce the weight of testis, epididymis and seminal vesicle by the rats. They also found a reduction of the epididymal sperm count, the level of testosterone, LH and FSH. These changes disappeared after some time. By the female rats, a decrease of the weight from the ovary and uterus was seen. There was also a decrease in the estrogen level. The litter number and weight were also reduced.
Insecticidal extracts of the bark were first used in the USA 1850 and 1880 in Europe.
Extracts of Quassia wood or bark act as a natural insecticide. For organic farming this is of particular interest. A good protection was shown against different insect pests (e.g. aphids, Colorado potato beetle, Anthonomus pomorum, Rhagoletis cerasi, Caterpillars of Tortricidae). Quassin extract works as a contact insecticide. Adverse effects on beneficial organisms were not found.
Quassia amara extract can be obtained by boiling Q.amara chips in water and removing the wood chips afterwards. The extract contains quassin and neoquassin, which have insecticidal properties. The extract can be used to spray fruitlets, shortly after cease blooming. Insecticidal effects are comparable to the insecticide diazinon. If the extract is sprayed before apple sawfly larvae hatched, Hoplocampa infestation can be reduced with an efficacy of 50%. Q.amara extract in the dosage corresponding to 3-4.5 kg of Q. amara wood chips for 1/ha is optimal. The bitter wood can be dried after boiling and be reused 2 to 3 times. The extract of Q.amara can be storaged over half a year (e.g. spring till autumn).
Q.amara is also used as a stomach or contact insecticide against various aphids and moths, potato beetle, apple blossom veevil and thephtid fruit fly. Q.amara extract possesses antiparasitic, antibacterial, amoebacidial, antiviral and anti-inflammatory properties.
Potential effects on human health
Like any poorly studied alternative chemical applied to food crops, Quassia extract may have unknown health consequences. A study on rats in 1997 found that Quassia extract significantly reduced their fertility, reducing testes size, sperm quality and serum testosterone.
Around 200 grams (7.1 oz) of Quassia wood chips are put together with 2 litres (0.44 imp gal; 0.53 US gal) of water. It is allowed to stand for 24 hours and then it is cooked for 30 min. It is then diluted with 10 to 20 litres (2.2 to 4.4 imp gal; 2.6 to 5.3 US gal) of water and used as a spray The use of approximately 3–4.5 kilograms (6.6–9.9 lb) wood extract per hectare seems to be optimal to minimize the damage of Hoplocampa testudinea on apple trees.
Seeds and cuttings can be used for propagation of Q. amara. Frost is not tolerated, but the plant is partially drought tolerant. A large amount of indirect light is recommended. As a tropical tree, Q. amara prefers a fertile, moist but well-drained soil in a partially shaded position. Although younger trees may tolerate greater or more direct light intensities, it is recommended for the agroecological cultivation of the plant’s wood, to plant Q. amara in settings that offer large amounts of indirect light.
The older the plant, the greater the accumulation of quassinoids in the xylem. Cultivation conditions, in the shade or in the sun, inﬂuences notably the amount of quassine accumulated by the plants. This factor will have to be taken into account to achieve a good harvest. Controlled luminosity conditions favor plant growth and the concentration of quassinoids in the tissues, which increases the quality of the raw material. Organic fertilizer such as deep or organic mulch can be used as nutritional compounds.
In Costa Rica the flowering period of Q.amara arises between October and April, whereas in central Panama the flowering period occurs from October to January. The fruits ripen after two months. In February and early March, there is a peak of fruit ripening. The drupes show different colors during the ripening process. They turn from reddish to green until the reach a black color. The best germination results were obtained with seeds from drupes that are just before becoming totally black. Not only the color but also the size of the fruits are indicators for the viability of a seed. Fruits with a size between 1 and 1.5 cm are suitable for reproduction and they can be easily detached from the receptacle.
The treelet can be propagated sexual by seeds or asexual by vegetative cuttings of half-ripe wood. The trees can be cultivated in tree nurseries. Therefore seeds can be sowed of substrat such as sawdust, sand or soil. The seedlings are grown up for eight months until they reach a height around 40 cm. The germination occurs within 10 weeks. During the germination period daily watering is important. A distance of 10 x 15 cm at a density of 35 plants per m is recommended in tree nurseries.
Pests and diseases
Cutting insects were found in seedlings, but no critical damage was observed. The fungus Colletotrichum sp. caused anthracnosis in young plants, what leads to brown leaf changes surrounded by a yellowish halo, defoliation and suspension of plant growth. High soil moisture, inadequate soil drainage, high sowing density and bad weed control management are factors that enhances this fungal disease. It can be controlled with specific funigcides. Bacteria infection is scarce, but has to be taken into account during the transplantation.
- Amargo – Quassia amara. Tropical Plant Database. 2013-02-11. Accessed 2017-09-07.
- Tree of the Month: Hombre Grande. Titi Conservation Alliance. Accessed 2017-09-08.
- Morton, Julia Frances, 1912- (1981). Atlas of medicinal plants of Middle America : Bahamas to Yucatan. Springfield, Ill.: C.C. Thomas. ISBN 978-0-398-08969-6. OCLC 849937602.CS1 maint: multiple names: authors list (link)
- Barwick, Margaret. (2004). Tropical & subtropical trees : a worldwide encyclopaedic guide. Van der Schans, Anton., Barwick Claudy, Jan. London: Thames & Hudson. ISBN 0-500-51181-0. OCLC 58457636.
- Paulo, Joana A.; Villalobos, Roger (2019-09-22). "Quassia amara L. diameter and total height under different light conditions: implications for the management of agroecosystems". Agroforestry Systems. 94 (3): 761–778. doi:10.1007/s10457-019-00446-9. ISSN 0167-4366. S2CID 202718128.
- Gilbert, B.; Favoreto, R. (September 2010). "Estado da Arte / State of the Art, Quassia amara L. (Simaroubaceae)". Revista Fitos. 5 Nº03 – via http://revistafitos.far.fiocruz.br/index.php/revista-fitos/article/view/118.CS1 maint: multiple names: authors list (link)
- Próspero, R.; Ming, L.C.; Rojas, R.D.; Ocampo, R.A. (2009). "Avaliação do incremento em volume de madeira de Quassia amara L.- Simaroubaceae, em cultivo agroecológico no trópico úmido da Costa Rica". Revista Brasileira de Plantas Medicinais. 11 (4): 450–454. doi:10.1590/S1516-05722009000400014. ISSN 1516-0572.
- Roubik, David W.; Holbrook, N. Michele; Parra, German V. (May 1985). "Roles of nectar robbers in reproduction of the tropical treelet Quassia amara (Simaroubaceae)". Oecologia. 66 (2): 161–167. Bibcode:1985Oecol..66..161R. doi:10.1007/bf00379850. ISSN 0029-8549. PMID 28311585. S2CID 5613537.
- Díaz, Roberto; Hernández, Lorena; Ocampo, Rafael; Cicció, José (2015-06-17). "Domesticación y fitoquímica de Quassia amara (Simaroubaceae) en el trópico húmedo de Costa Rica". Lankesteriana. 6 (2). doi:10.15517/lank.v6i2.19702. ISSN 2215-2067.
- Villalobos, R.; D. Marmillod; R. Ocampo (1997). "Variation in the quassin and neoquassin content in Quassia amara (Simaroubaceae) in Costa Rica: Ecological and management implications". Acta Horticulturae. 502. Retrieved 4 November 2012.
- "Amargo". Archived from the original on 20 December 2012. Retrieved 4 November 2012.
- S. Bertani; E. Houël; D. Stien; L. Chevolot; V. Jullian; G. Garavito; G. Bourdy E. Deharo (2006). "Simalikalactone D is responsible for the antimalarial properties of an amazonian traditional remedy made with Quassia amara L. (Simaroubaceae)". Journal of Ethnopharmacology. 108 (1): 155–157. doi:10.1016/j.jep.2006.04.017. PMID 16730421.
- Ferrari, A; Diehl, C (2012). "Evaluation of the efficacy and tolerance of a topical gel with 4% quassia extract in the treatment of rosacea". J Clin Pharmacol. 52 (1): 84–8. doi:10.1177/0091270010391533. PMID 21343346. S2CID 29876609.
- Cachet, N.; Hoakwie, F.; Bertani, S.; Bourdy, G.; Deharo, E.; Stien, D.; Houel, E.; Gornitzka, H.; Fillaux, J.; Chevalley, S.; Valentin, A. (2009-10-01). "Antimalarial Activity of Simalikalactone E, a New Quassinoid from Quassia amara L. (Simaroubaceae)". Antimicrobial Agents and Chemotherapy. 53 (10): 4393–4398. doi:10.1128/AAC.00951-09. ISSN 0066-4804. PMC 2764154. PMID 19667291.
- "What are the Uses and Benefits of Quassia Amara- Herb?". Planet Ayurveda. 2019-07-27. Retrieved 2019-11-08.
- "Quassia". Medisite (in French). Retrieved 2019-11-08.
- "Quassia Amara" (PDF).
- "What is Quassia Amara? (with pictures)". wiseGEEK. Retrieved 2019-11-18.
- "Quassia facts and health benefits". Retrieved 2019-11-13.
- Husain, Gulam Mohammed; Singh, Paras Nath; Singh, Rakesh Kumar; Kumar, Vikas (2011). "Antidiabetic Activity of Standardized Extract of Quassia amara in Nicotinamide–Streptozotocin-induced Diabetic Rats". Phytotherapy Research. 25 (12): 1806–1812. doi:10.1002/ptr.3491. ISSN 1099-1573. PMID 21480415. S2CID 20916275.
- Ferreira, S.F.; Azevedo, S.C.S.F.; Vardanega-Peicher, M.; Pagadigorria, C.L.S.; Garcia, R.F. (2013). "Anti-hiperglycemic effect of Quassia amara (Simaroubaceae) in normal and diabetic rats". Revista Brasileira de Plantas Medicinais. 15 (3): 368–372. doi:10.1590/s1516-05722013000300009. ISSN 1516-0572.
- Bertani, S.; Houël, E.; Stien, D.; Chevolot, L.; Jullian, V.; Garavito, G.; Bourdy, G.; Deharo, E. (2006). "Simalikalactone D is responsible for the antimalarial properties of an amazonian traditional remedy made with Quassia amara L. (Simaroubaceae)". Journal of Ethnopharmacology. 108 (1): 155–157. doi:10.1016/j.jep.2006.04.017. PMID 16730421.
- Ajaiyeoba, E.O; Abalogu, U.I; Krebs, H.C; Oduola, A.M.J (1999). "In vivo antimalarial activities of Quassia amara and Quassia undulata plant extracts in mice". Journal of Ethnopharmacology. 67 (3): 321–325. doi:10.1016/s0378-8741(99)00073-2. ISSN 0378-8741. PMID 10617067.
- Raji, Yinusa (2013-01-24). Effects of bioactive principles from stem bark extract of Quassia amara , Quassin and 2-methoxycanthine-6-one, on haematological parameters in albino rats. Physiological Society of Nigeria. OCLC 834050831.
- García-Barrantes, Pedro Manuel; Badilla, Beatriz (2011). "Anti-ulcerogenic properties of Quassia amara L. (Simaroubaceae) standardized extracts in rodent models". Journal of Ethnopharmacology. 134 (3): 904–910. doi:10.1016/j.jep.2011.01.052. ISSN 0378-8741. PMID 21296139.
- Raji, Y; Oloyede, GK (2011-10-05). "Antiulcerogenic Effects and Possible Mechanism of Action of Quassia Amara (L. Simaroubaceae) Extract and Its Bioactive Principles in Rats". African Journal of Traditional, Complementary and Alternative Medicines. 9 (1): 112–119. doi:10.4314/ajtcam.v9i1.16. ISSN 0189-6016. PMC 3746530. PMID 23983328.
- KUPCHAN, S. M.; STREELMAN, D. R. (1977-02-08). "ChemInform Abstract: QUASSIMARIN, A NEW ANTILEUKEMIC QUASSINOID FROM QUASSIA AMARA". Chemischer Informationsdienst. 8 (6): no. doi:10.1002/chin.197706323. ISSN 0009-2975.
- "Quassia". RAUSCH AG Kreuzlingen (in French). Retrieved 2019-11-08.
- Toma, W; Gracioso, J.S; Hiruma-Lima, C.A; Andrade, F.D.P; Vilegas, W; Souza Brito, A.R.M (2003). "Evaluation of the analgesic and antiedematogenic activities of Quassia amara bark extract". Journal of Ethnopharmacology. 85 (1): 19–23. doi:10.1016/S0378-8741(02)00334-3. PMID 12576198.
- "Quassia - Définition et recettes de "Quassia"". Supertoinette (in French). Retrieved 2019-11-08.
- Raji, Yinusa; Bolarinwa, Adeyombo F. (1997). "Antifertility activity of Quassia amara in male rats — In vivo study". Life Sciences. 61 (11): 1067–1074. doi:10.1016/s0024-3205(97)00615-2. ISSN 0024-3205. PMID 9307052.
- Njar, Vincent; Alao, Taiwo; Okogun, Joseph; Raji, Yinusa; Bolarinwa, Adeyombo; Nduka, Ebere (1995). "Antifertility Activity ofQuassia amara: Quassin Inhibits the Steroidogenesis in Rat Leydig CellsIn Vitro". Planta Medica. 61 (2): 180–182. doi:10.1055/s-2006-958044. ISSN 0032-0943. PMID 7753928.
- Parveen, S (2003). "A comprehensive evaluation of the reproductive toxicity of Quassia amara in male rats". Reproductive Toxicology. 17 (1): 45–50. doi:10.1016/s0890-6238(02)00080-1. ISSN 0890-6238. PMID 12507657.
- Yinusa, Raji Adeniran, Akinola Oyeyipo, P Ibukun Omowumi, Femi-Akinlosotu (2013-01-18). Reproductive activities of female albino rats treated with quassin, a bioactive triterpenoid from stem bark extract of Quassia amara. Nigerian Journal of Physiological Sciences. OCLC 839270740.CS1 maint: multiple names: authors list (link)
- "Quassia-Bitterholz". Ökologischer Landbau. Archived from the original on 31 December 2013. Retrieved 3 November 2012.
- EGGLER, B.D.; GROß, A. (1996): Quassia-Extrakt; neue Erkenntnisse bei der Regulierung von Schaderregern im Obstbau. Mitt. d. Biol. Bundesanst., 321, 425
- Zijp, J. P.; Blommers, L. H. M. (2002). "Apple sawfly Hoplocampa testudinea (Hym., Tenthredinidae) and its parasitoid Lathrolestes ensator in Dutch apple orchards (Hym., Ichneumonidae, Ctenopelmatinae)". Journal of Applied Entomology. 126 (6): 265–274. doi:10.1046/j.1439-0418.2002.00665.x. ISSN 1439-0418. S2CID 85567972.
- "Acta Horticulturae". www.actahort.org. Retrieved 2019-11-10.
- "Article". Horticultural Science. doi:10.17221/76/2009-hortsci.
- Graf, B.; Höpli, H. U.; Höhn, H. (2002). "The apple sawfly, Hoplocampa testudinea: egg development and forecasting of egg hatch". Entomologia Experimentalis et Applicata. 105 (1): 55–60. doi:10.1046/j.1570-7458.2002.01032.x. ISSN 1570-7458. S2CID 83626961.
- KREUTER, M.-L. (1995): Pflanzenschutz im Bio-Garten. BLV, München Wien Zürich, 249 S.
- SCHMID, O., HENGGELER, S. (1989): Biologischer Pflanzenschutz im Garten. Stuttgart: Ulmer, 270 S.
- EGGLER, B.D.; GROß, A.; TRAUTMANN, M. (1992): Biologisch aktive Pflanzenauszüge; eine natürliche Alternative bei der Behandlung von Schaderregern im Obstbau. 5. Internationaler Erfahrungsaustausch über Forschungsergebnisse zum Ökologischen Obstbau, 19. und 20.11.1992, Hrsg. Fördergemeinschaft Ökologischer Obstbau, Baden-Württemberg, Ministerium für ländlichen Raum, Landwirtschaft und Forsten, 28
- HÖHN, H.; HÖPLI, H. U.; GRAF, B. (1996): Quassia und Neem: exotische Insektizide im Obstbau. Schweiz. Z. Obst-Weinbau, 3, 62-63
- GROß, A., EGGLER, B.D. (1993): Möglichkeiten zur vorbeugenden Behandlung gegen die Kirschfruchtfliege mit Quassia amara. 6. Internationaler Erfahrungsaustausch über Forschungsergebnisse zum Ökologischen Obstbau, 18 und 19.11.1993, Hrsg. Fördergemeinschaft Ökologischer Obstbau, Baden-Württemberg, Ministerium für ländlichen Raum, Landwirtschaft und Forsten, 50
- Ajaiyeoba, E. O.; Krebs, H. C. (December 2003). "Antibacterial and antifungal activities of Quassia undulata and Quassia amara extracts in vitro". African Journal of Medicine and Medical Sciences. 32 (4): 353–356. ISSN 0309-3913. PMID 15259916.
- "ANTIMICROBIAL ACTIVITY OF THE ETHANOLIC EXTRACT FROM Quassia amara, Solanum sciadostylis AND Artemisia annua ON GRAM NEGATIVE BACTERIAL | Galoá Proceedings". proceedings.science. Retrieved 2019-11-10.
- Raji, Y; Bolarinwa AF (1997). "Antifertility activity of Quassia amara in male rats - in vivo study". Life Sciences. 61 (11): 1067–74. doi:10.1016/S0024-3205(97)00615-2. PMID 9307052.
- Psota, V.; J. Ourednickova; V. Falta (2010). "Control of Hoplocampa testudinea using the extract from Quassia amara in organic apple growing" (PDF). Horticultural Science. 37: 139–144. doi:10.17221/76/2009-HORTSCI.
- "Quassia amara". tropilab. Retrieved 3 November 2012.
- Claire, Daniel. "Agroecological Growth Patterns of Cultivated Bitterwood (Quassia amara) on the Northwestern Caribbean Slope of Costa Rica" (PDF). Retrieved 4 November 2012.