Cashew (Anacardium occidentale)

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Cashew Tree Summary

The cashew plant is a large Amazonian tree growing throughout South America. It favours the drier, sandier regions of the central plains of Brazil, but can also be found growing deep within the Amazon rainforest.

The fruit is well known across the world for its delicious flavour and high protein content. Medicinally, the leaves, bark, and pseudo-fruit are more important.

The leaves are used during radiation therapy for cancer as an adjunctive treatment, and have a positive impact on glucose regulation as well making them useful for both type I and type II diabetics.

The bark is highly astringent, and therefore reliable as a treatment for acute diarrhea. This part of the tree is also commonly used as a hypotensive agent to lower blood pressure.

 

+ Indications

  • As a prebiotic
  • Bacterial infection
  • Bladder stones
  • Cardiovascular disease
  • Colic
  • Dermatitis
  • Diabetes
  • Diarrhea
  • Hepatitis C
  • Hypertension
  • Kidney stones
  • Mouth ulcers
  • Oxidative damage protection
  • Periodontal disease
  • Radiation therapy
  • Stomach ulcers
  • Urinary tract infection

+ Contraindications

  • None noted

Herbal Actions:

  • Hypocholesterolemic
  • Antidiabetic
  • Anti-Inflammatory
  • Antimicrobial
  • Antitumor
  • Antiviral (HCV)
  • Astringent
  • Cardio-Inhibitory
  • Hypotensive
  • Nutritive
 

What Is Cashew Used For?

The leaves and bark are used to treat diabetes, diarrhea, colic, urinary tract infections, hepatitis C, mouth ulcers, stomach ulcers, hypertension, and cardiovascular disease.

The pseudofruit is mainly used for its antitumor action, as a supportive agent during radiation therapy. It is also an antimicrobial and prebiotic agent useful for inhibiting urease and lipoxygenase activity.

 

Traditional Uses

+ South America

Indigenous cultures of the Amazon rain forest, have used A. occidentale medicinally for hundreds of years, and has been cultivated by them for use as well. Amazonian indigenous cultures have used this plants various parts for different uses. The bark was used for diarrhea, colic for infants, as a douche, astringent, tooth extraction post treatments, diabetes, weakness, muscular debility, urinary disorders, asthma [15].

The leaves were used most commonly as a tea referred to as casho, and was employed for such uses as diarrhea treatment, mouth ulcers, tonsillitis, throat problems, washing wounds. Both the leaves and the bark were used interchangeably for such uses as treating eczema, psoriasis, scrofula, dyspepsia, genital problems and STIs, impotence, bronchitis, colic, diarrhea, and as a general tonic [15].

The fruit and fruit juice were used for influenza, diarrhea, syphilis, as a stimulant, diuretic, and aphrodisiac, and in the 1600s, in Brazil, Europeans were taking cashew juice to treat fever, to sweeten the breath, and to “conserve the stomach” [15].

The toxic seed oil has been used traditionally as a topical remedy for botfly larvae [15].

Brazil uses the leaves for eczema, psoriasis, scrofula, dyspepsia, genital problems, and venereal diseases, as well as for impotence, bronchitis, cough, intestinal colic, leishmaniasis, and syphilis-related skin disorders [16].

 

Weekly Dose

Part Used

Fruit, pseudofruit, leaves, bark.

Family Name

Anacardiaceae

Distribution

South America (Central plains)

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Constituents of Interest

  • Anacardic acids
  • Anacardol

Common Names

CYP450

  • Unknown

Quality

  • Unknown

Pregnancy

  • Unknown

Taste

  • Unknown

Duration of Use

  • Long term use is acceptable.
 

Botanical Information

The cashew tree is a member of the anacardiaceae family of plants, which includes 9 other species. The tree is large and arromatic, growing up to 15m high.

The cashew nut, most commonly known internationally, is the fruit of the plant. It grows inside a capsule filled with toxic irritating latex. Behind the fruit grows a large swollen peduncle (called a pseudofruit) that contains a sweet tasting juice high in minerals and vitamin C.

The leaves are described as clustered (at shoot apex), simple, entire, and usually have a rounded apex. [13].

The inflorescences are either terminal or axillary, and paniculate. Anacardium spp. contains both bisexual, and unisexual flowers on the same tree. The flowers are 5 petaled, 6-12 stamens, with 1 or 4 of them much longer than the others with the shorter stamens below fused to form a short tube. The flowers may or may not have anthers [13].

Medicinally, the bark, leaves, pseudo-fruit, and seed (nut/fruit) are all used [15].

A. microcarpum, is also edible, and is starting to gain interest for this purpose in Brazil, and other South American countries, the author at this time however has not found any quality research suggesting its use as a safe alternative, for the known medicinal A. occidentale.

 

Habitat, Ecology, Distribution

Anacardium spp, is indigenous to the Amazon rainforest, specifically, from Honduras to Paraguay and southern Brazil, with A. occidentale favouring the drier, sandy soils in the central Plains of Brazil, and northern South America, [13, 15]. Currently, A. occidentale is widely cultivated in Peru, and other lowland Amazonia, mostly for its hydrocarp, and fruit [13]. The cultivation of A. occidentale is estimated to cover approximately 700 000 hectares (7000 square kilometers), with nut production at about 280 000 tons/year (255000 metric tonnes) [4]. In Brazil, the vast majority of production (96%) takes place in the northeast region of the country [4]. This plant has huge economical impact on the regions cultivating it, due to the large labor force required to cultivate, and process it [4].

Upon discovery by the Europeans, the cashew tree was exported to India, and East Africa where it has since become naturalized [15].

 

Other Common Names

Caueiro, Cashew, Cashu, Casho, Acajuiba, Caju, Acajou, Acaju, Acajaiba, Alcayoiba, Anacarde, Anacardier, Anacardo, Cacajuil, Cajou, Gajus, Jocote maranon, Maranon, Merey, Noix d’acajou, Pomme cajou, Pomme, Jambu, Jambu golok, Jambu mete, Jambu monyet, Jambu terong.

 

Pharmacology & Medical Research

+ Diabetes

L. A study done on Anacardium occidentale and its effects on diabetes, and found that the long term efficacy of a hexane extract (leaves) acted as a hypoglycemic agent in diabetic rats. [10].

An ethanol extract of the stem bark showed no hypoglycemic effects on type 1 diabetic rats, or type 2 diabetic rats in fasting condition, however did show significant hypoglycemic effects in type 2 diabetic rats when fed glucose simultaneously. These results were suggested to be due to insulin stimulating actions in a glucose dependant manner in the pancreas, as well as possible inhibition of glucose absorption in the gastrointestinal tract (Ramnik Singh, 2010). These findings suggest the best time to take this herb for treatment in diabetes, may be with meals.

Anacardium humile stems have also been shown to produce significant antidiabetic effects, regulating blood sugar levels in diabetic rats, though did not alter insulin secretion. This extract (aqueous) also showed no toxicity [12]. This species needs closer examination to identify how it compares to A. occidentale.

+ Diarrhea

Tannins have been found in the bark, and leaves of the cashew tree [15]. These chemicals have a proven effect on astringing the digestive tract, and therefore produce anti-diarrhea actions.

+ Cancer

Anacardic acid is associated with A. occidentales antitumor effects [9]. One study [2] suggested that “one possible mechanism by which anacardic acid exerts its effects is by modulating the nuclear factor-κB”. Various inflammatory agents induce activation of this protein complex, including cytokines, carcinogens, cigarette smoke, stress, and environmental pollutants. Due to the various negative effects associated with the activation of this complex (such as various tumor cell promoting effects), suitable inhibitors are actively being researched, including A. occidentale extracts.

Lucio Neto et al., (2013) reports that “anacardic acid has been shown to be cytotoxic to lung, liver and gastric tumor cells through epigenetic mechanisms by inhibiting histone acetyl-transferases (HATs)” [11].

Anacardic acid has also been shown to potentiate apoptosis induced by TNF [2].

This constituent, which can be found in a variety of plants, has been shown to also exhibit actions that sensitize tumors to radiation [2], which may increase the efficacy of radiation therapy cancer treatment.

A. De Sousa Leite et al, (2015), investigated the effects of natural cashew nut shell liquid (iCNSL) (only heated to 45C), and technical cashew nut shell liquid (tCNSL) (heated to 195C for 3 hours), on genotoxicity. They discovered that the lowest concentrations of iCNSL and all concentrations of tCNSL provided preventive, antimutagenic, and reparative effects on micronuclei and on chromosomal aberration. The tCNSL was reported to be not toxic, cytotoxic, or mutagenic in any of the concentrations [1].

These combined effects, may prove Anacardium occidentale efficacious in the treatment of various cancers.

+ Hypertension

A bark stem extract of A. occidentale was shown to produce anti hypotensive effects in vivo [5].

+ Inflammation

Listed in the Nigerian, and Brazilian traditional pharmacopoeia for its anti inflammatory effects [10]. These effects are at least partly due to its anacardic acid content, which has been demonstrated to produce anti inflammatory actions, as well as many more effects [9]. These effects are thought to be due to modulation of nuclear factor-κB [2] which plays a key role in the process of inflammation.

+ Antimicrobial

A. occidentale fruit has been shown to produce antimicrobial effects against Helicobacter pylori [15]. Anacardic acid, contained in this plant, have demonstrated antimicrobial effects [9], and may at least in part be responsible for this action from the plant or plant extract.

Cosmetically, extracts from A. occidentale pseudo-fruits, demonstrated antimicrobial actions, however were considered unstable, forming crusts on the surface of the formulas. Researchers in this study suggested the addition of antioxidant substances may ameliorate this instability but suggested more research in this area was required [7].

In a study done by G. Anand et al., (2015), identifying the antimicrobial effects of A. occidentale in the form of an oral mouthwash, noted the significant antifungal, and antibacterial effects that were considered equal, or greater than povidone-iodine rinses currently used today. Some of the pathogens of note in oral health are Enterococcus faecalis, Staphylococcus aureus, Streptococcus mutans, Escherichia coli, and Candida albicans due to the common resistance these pathogens have against normal oral care products. This study showed that the ethanol extract of A. occidentale showed significant in vitro activity against all of these organisms, as well as MRSA [6].

+ Cardiovascular

A stem bark extract has been shown to produce cardio-inhibitory effects in vitro and was suggested to be due to either calcium channel blockage, or hindrance of calcium release from internal storages, or a combination of both [5]. More research is needed in this area to determine the exact mechanism of action, however it is clear that A. occidentale bark stem extract has a positive effect on hypertension, and CVD.

+ Hepatitis C

Hepatitis C is a virus in the genus Hepacivirus contained within the Flaviviridae family. This infection can become chronic, and will eventually lead to cirrhosis of the liver, hepatocarcinoma, and eventually death by liver failure. The World Health Organization suggests more than 120-150 million people worldwide are infected with this virus,and the numbers are growing. About 500 000 people die each year as a result of this infection [18].

Anacardic acid has been shown to inhibit HCV entry, replication, translation, and virion secretion in a dose dependant action and has no reported toxicity, or measurable effects on cell viability [9]. These researchers suggested the mechanism of action be due to anacardic acids ability to inhibit histone acetyltransferases (HATs). The dose focused specifically on anacardic acid (>5µM) and needed to be administered over multiple hours (12h) to produce the significant effects noted in the study. These researchers did not specify how the anacardic acid was administered, however it is most likely intravenous. This brings up the question of how long, and in what concentrations anacardic acid will remain active in the system from oral administration, and if these demonstrated therapeutic effects can be recreated through oral ingestion of A. occidentale extract. More research is needed to better understand this mechanism of action. Researchers need to investigate further whether these effects can be translated to other members of the Flaviviridae family, or other viruses in general.

Other members of this family (Flaviviridae), include yellow fever, dengue fever, and arboviruses [17].

+ Nutritive

Cashew nuts nutritional profile per 100g is as follows: 2314 kJ of energy, 46.4g of fat, 9.2g saturated fatty acids, 27.3g monounsaturated fatty acids, and 7.8g polyunsaturated fatty acids, 7.7g linoleic acid, 0.15g α-linolenic acid, 18.2g protein, 5.9g fiber, 25μg folate, 158 mg plant sterols, 37mg Ca, 292 mg Mg, 12 mg Na, 660 mg K [3].

Nuts in general are considered an energy dense food, and have been reported to positively affect coronary heart disease, high cholesterol, and diabetes with their consumption. Nutritionally, cashews in particular contain significant amounts of plant protein, α-linolenic acid, plant sterols (not including cholesterol), Mg, Na, and K as compared to other nuts [3].

+ Prebiotic

In order to be considered a prebiotic oligosaccharide, it must:

  1. Not be absorbable by the upper GI tract
  2. Be a selective substrate for beneficial bacteria in the gut
  3. Promote healthy intestinal biota

With this in mind, A. occidentale fermented pseudo-fruit juice has been shown to meet these requirements to be considered as a prebiotic source [8].

 

Phytochemistry

The pseudo-fruit, contains rich amounts of minerals, vitamins, esters, terpenes, and carboxylic acids [15].

The bark and leaves contain tannins, which have been the subject of much scientific study, and due to the astringency associated with this chemical, may account for the antidiarrheal effects of this plant [15].

The nutshells contain anacardic acids in high amounts, which have been shown to produce cytotoxicity to certain cancer cells, and curb the darkening effect of aging through tyrosinase inhibition [15].

The pseudo-fruit (cashew apple) contains volatile compounds, resorcinolic acid, anacardic acids, carotenoids (α-carotene, β-carotene and β-cryptoxanthin), vitamin C, phenols, tannin and two flavonoid aglycones. Phenolic constituents include anacardic acids, cardols, and cardanols [4].

+ Anacardic Acid

Anacardic acid (found in high amounts in the nutshell), has been found to inhibit the activity of various cellular enzymes, including histone acetyltransferases (HATs) [9]. Anacardic acid can also be found in Ginkgo biloba, Amphipterygeum adstringens, and Ozoroa insignis [9]. This compound has been shown to produce numerous medicinal actions such as anti inflammatory, antimicrobial, antioxidant, and antitumor activities [9]. It has also been shown to inhibit numerous other enzymes, including tyrosinase (also associated with cytotoxicity), xanthine oxidase (likely cause for low shelf life of juice), phosphatidylinositol-specific phospholipase C, tissue factor VIIa, lipoxygenase, and cyclooxygenase (COX) [2]. The nut shell liquid, contains high amounts of cardol, and cardanol as well.

+ Cashew Shell Latex

A. De Sousa Leite et al, (2015), reports the concentrations in the natural cashew nut shell liquid extracted via solvents (referred to as iCNSL) (highest temperature reached in the making of this extract was 45C) as 62.9% anacardic acid, 23.98% cardol, and 6.99% cardanol. A different extraction process referred to as technical cashew nut shell liquid (tCNSL) is achieved by burning the nuts at high temperatures (195C bath for 3 hours), which in turn changes these amount to 60-65% cardanol, 15-20% cardol, 10% polymeric material, and small amounts of melticardol. This process of burning the nuts decarboxylates the anacardic acid (removes acid group), and converts this compound into cardanol. [1].

+ Cashew Apple Juice

Interestingly, E.S. De Brito et al., (2007) reports that both cashew apple (pseudo-fruit) and cranberry contained the same set of 12 glycosylated flavonols, namely, 3-O- galactoside, 3-O-glucoside, 3-O-xylopyranoside, 3-O-arabinopyranoside, 3-O- arabinofuranoside and 3-O-rhamnoside of myricetin and quercetin. [4].

It would be interesting to examine the comparative effects of these two botanicals to determine possible effects of these chemicals and their synergy.

+ Summary Of Constituents

Taylor L. (2005), describes the main chemicals contained within A. occidentale as follows: alanine, alpha-catechin, alpha-linolenic acid, anacardic acids, anacardol, antimony, arabinose, caprylic acid, cardanol, cardol, europium, folacin, gadoleic acid, gallic acid, ginkgol, glucuronic acid, glutamic acid, hafnium, hexanal, histidine, hydroxybenzoic acid, isoleucine, kaempferol-epicatechin, lauric acid, leucine, leucocyanidin, leucopelargonidine, limonene, linoleic acid, methyl-glucuronic acid, myristic acid, naringenin, oleic acid, oxalic acid, palmitic acid, palmitoleic acid, phenylalanine, phytosterols, proline, quercetin-glycoside, salicylic acid, samarium, scandium, serine, squalene, stearic acid, tannin, and trans-hex-2-enal tryptophan. [15].

 

Clinical Applications Of The Cashew Plant:

The most clinically relevant uses of the cashew tree involve its antimicrobial actions, both topically and internally for both bacterium and virus, as well as its glucose regulating actions, and hypotensive effects on the cardiovascular system.

There has been some compelling evidence for its use as an adjunctive cancer treatment in recent years as well.

The barks astringing qualities makes it reliable for treating diarrhea.

 

Cautions:

Cardol contained withing the cashew fruits shell is caustic and toxic. All cashews are first heated to destroy this compound before consumption.

 

Synergy

A combination of Anacardium occidentale (stem bark, and leaf extract), Eucalyptus globulus, Psidium guajava (leaves), and Xylopia aethiopaca (fruits), were found to produce synergistic action on the treatment of diabetes [16].

 

Author

Justin Cooke, BHSc

The Sunlight Experiment

(Updated November 2018)

 

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References:

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