Understanding Anthraquinones
Anthraquinones are a large group of naturally occurring organic compounds found in many plants, fungi, and some insects. Chemically, they are derivatives of 9,10-anthracenedione and are often present as glycosides, which means they are bonded to a sugar molecule. These glycosides are typically inactive until they reach the large intestine, where bacteria hydrolyze them into their active forms (aglycones). The therapeutic benefit most famously associated with anthraquinones is their potent stimulant laxative effect, which works by irritating the lining of the colon to promote muscle contractions (peristalsis) and increase fluid content. However, anthraquinones also possess other pharmacological activities, such as anti-inflammatory, antimicrobial, and antioxidant effects.
Common Food and Plant Sources of Anthraquinone
Aloe Vera
Aloe vera contains anthraquinone derivatives, primarily in the bitter, yellow latex found in the thin layer between the outer green skin and the inner clear gel. Aloin, specifically the isomers Aloin A (barbaloin) and Aloin B (isobarbaloin), is the most prevalent anthraquinone compound in aloe latex. The concentration of these compounds can be significantly reduced or completely removed during processing, particularly in commercially available aloe gel products intended for consumption. In contrast, unfiltered whole leaf extracts will contain higher levels of anthraquinones, which can cause severe cramping and diarrhea.
Senna
Senna is one of the most well-known botanical sources of anthraquinone, derived from the leaves and fruit of the Cassia plant. The primary active components are dianthrone glycosides known as sennosides (A, B, C, and D). These compounds are highly effective stimulant laxatives and are widely used in over-the-counter and prescription medications for treating constipation. Senna preparations are not recommended for long-term use due to the risk of dependency and other adverse effects.
Rhubarb
The root and rhizome of rhubarb (Rheum species), a popular medicinal herb in Chinese medicine, are rich in anthraquinone glycosides. Notable compounds include rhein, emodin, aloe-emodin, chrysophanol, and physcion. The laxative properties of rhubarb are primarily due to sennosides, similar to those found in senna. Interestingly, the composition and concentration of anthraquinones in rhubarb can vary significantly based on factors like altitude, with plants grown at higher altitudes often having higher anthraquinone content. The rhubarb stalks typically used in culinary applications contain much lower levels and do not have the same laxative effect.
Cascara Sagrada
Known as "sacred bark," cascara sagrada is the dried bark of the California buckthorn (Rhamnus purshiana). It contains anthraquinone glycosides called cascarosides, which have powerful laxative effects. Due to safety concerns, the U.S. Food and Drug Administration (FDA) ruled that cascara sagrada and certain other anthraquinone stimulant laxatives are not generally recognized as safe and effective for over-the-counter use, though it is still available as an herbal supplement.
Other Sources
Other plant and non-plant foods containing anthraquinones include:
- Yellow Dock: The root of the yellow dock plant (Rumex crispus) contains anthraquinones, though it is considered milder than senna or cascara, especially when aged.
- Frangula: The bark of Frangula alnus contains anthraquinone glycosides, used traditionally as a laxative.
- Fermented Products: Some traditionally fermented foods, like Fuzhuan brick-tea, have been shown to contain anthraquinones produced by microbial populations during fermentation.
- Insects: Historically, certain insects, such as cochineal, were used to produce anthraquinone-derived dyes for food and other purposes.
Potential Health Risks and Safe Consumption
While anthraquinones offer certain medicinal benefits, particularly for short-term constipation relief, their use is associated with several health risks, especially with prolonged or high-dose intake. The main concerns include:
- Gastrointestinal Distress: Abdominal cramps, diarrhea, and nausea are common side effects due to the irritation of the intestinal lining.
- Electrolyte Imbalance: Prolonged use and diarrhea can lead to a loss of essential electrolytes, notably potassium (hypokalemia), which can cause serious health issues.
- Melanosis Coli: This condition involves a dark, brownish-black pigmentation of the colon lining, which develops after chronic use of anthraquinone laxatives. While historically considered benign, some research suggests a potential link to increased cancer risk.
- Carcinogenic Potential: Studies in animals have raised concerns about the carcinogenic potential of certain anthraquinone compounds. As a result, the International Agency for Research on Cancer (IARC) classifies some anthraquinones as “possibly carcinogenic to humans”.
- Dependence: The regular, long-term use of stimulant anthraquinone laxatives can lead to laxative dependence, where the bowel becomes reliant on the stimulant to function normally.
For these reasons, it is crucial to use anthraquinone-containing herbs and supplements sparingly and under the guidance of a healthcare professional. For everyday constipation relief, higher-fiber foods and other gentle options are generally safer.
Navigating Foods Containing Anthraquinone
| Source | Primary Anthraquinone Compound(s) | Associated Laxative Effect | Key Use |
|---|---|---|---|
| Aloe Latex | Aloin, Barbaloin, Aloe-Emodin | Strong | Medicinal (laxative) |
| Senna (Leaves/Fruit) | Sennosides A & B | Strong | Medicinal (laxative/cathartic) |
| Cascara Sagrada (Bark) | Cascarosides | Strong | Medicinal (laxative) |
| Rhubarb (Root) | Sennosides, Rhein Anthrone | Moderate to strong | Medicinal (laxative) |
| Yellow Dock (Aged Root) | Emodin, Chrysophanol | Mild | Medicinal (mild laxative) |
For those seeking anthraquinone-free food options or milder alternatives:
- Select Processed Aloe: Always choose reputable brands that clearly state the anthraquinones have been removed. The bitter yellow latex is the part to avoid.
- Distinguish Rhubarb Parts: Enjoy the stalks of rhubarb, as they do not contain significant levels of anthraquinones. Avoid the root, which is used medicinally.
- Consider High-Fiber Alternatives: For digestive health, opt for natural fiber-rich foods like fruits, vegetables, and whole grains, which promote regularity gently and without the risks associated with stimulant laxatives.
Conclusion
Anthraquinones are powerful, naturally occurring compounds found in several plants, including aloe, senna, rhubarb, and cascara sagrada, renowned for their stimulant laxative effects. However, their medicinal use, especially chronic or high-dose intake, carries risks, including gastrointestinal discomfort, potential dependence, and a link to serious health concerns in long-term use. For this reason, it is vital to approach these natural sources with caution and to consult a healthcare provider for any long-term digestive issues. While specific plant parts like rhubarb stalks and processed aloe gel are safe for general consumption, the medicinal use of anthraquinone-rich herbs should be carefully managed to ensure safety and prevent adverse health outcomes.
Rubia Tinctorum, Morinda Officinalis and Anthraquinones - NCBI
