Senna alexandrina

Senna Alexandria is a plant containing Sennosides, which are laxatives. Nothing more special about Senna root or Sennosides, they just are very effective at clearing your bowels and are at a level of potency where they are sometimes given before a colonoscopy.

This page features 41 unique references to scientific papers.

How to Take

Recommended dosage, active amounts, other details

In accordance with clinical usage, the correct dose is the "lowest dose required to produce the desired effects (soft-formed and comfortable stool)". This is either 1-2g of the powdered extract or fruit usually standardized to 10-30mg active Sennosides.

Higher doses are used only if the aforementioned lower dose is not effective (it should be noted that senna alexandria is a delayed laxative unlike the immediate effects of Caffeine and it may take a few hours to assess whether a dose is effective or not).

Senna alexandria tends to be taken prior to bed in order to time its laxative effect with a morning bowel movement.

Human Effect Matrix

The Human Effect Matrix looks at human studies (it excludes animal and in vitro studies) to tell you what effects senna alexandrina has on your body, and how strong these effects are.

Grade Level of Evidence
Robust research conducted with repeated double-blind clinical trials
Multiple studies where at least two are double-blind and placebo controlled
Single double-blind study or multiple cohort studies
Uncontrolled or observational studies only
Amount of Evidence
? The amount of high quality evidence. The more evidence, the more we can trust the results.
Outcome Magnitude of effect
? The strength of the outcome. Some supplements can have an increasing effect, others have a decrease effect, and others have no effect.
Consistency of research results
? Scientific research does not always agree. HIGH or VERY HIGH means that most of the scientific research agrees.
Constipation Strong Very High See all 6 studies
Due to the strong laxative effect, constipation is greatly reduced with supplemental Senna Alexandria. Has been noted effective against regular, postpartum, and opioid-induced constipation and appears to not require a context-specific cause of constipation (ie. reliable) but appears to be associated with more cramping than placebo.
Intestinal Motility Strong Very High See all 10 studies
Senna Alexandria is a reference drug for its laxative effects, with comparable efficacy to oral polyethylene glycol (PEG; used before colonoscopies) and lactulose, but more cost-effective than the latter

1Sources and Structure

1.1. Sources

It is sometimes traditionally referred to as . It has traditionally been used as a laxative which is clinically supported, and has further been claimed to be an expectorant, a wound dressing, an antidysenteric, and a carminative agent; and for the treatment of gonorrhoea, skin diseases, dyspepsia, fever, and haemorrhoids. None of these latter claims are scientifically validated yet.[1]

The active ingredients can also be derived from the fruits of Cassia angustifolia or acutifolia (considered synonymous),[2] the fruits of which are sometimes referred to as Fructus Sennae.[1] Rhubarb also has a small sennoside content,[3] at around 0.5%.[3][4]

1.2. Structure and Composition

As a herbal supplement, Senna contains a variety of molecules and bioactives such as:

  • The stereoisomers Sennoside A and B (main two, although C-E),[5][6] found at 1.12-1.24%[4]

  • Aloe-emodin and Emodin

  • Chrysophanol, Physcion and Racemochrysone, dihydroanthracenone and anthraquinone derivates[7]

  • Flavonoids, including Kaempferol[8]

  • Naphthalene precursors[8][9]

  • Beta-sitosterol and stigmasterol[7]

The sennosides are seen as the active ingredients, and are pictured below. They are glycosides of a rhein anthrone molecule, which then bind to each other in pairs. For the drug to be bioactive, the glycoside must first be broken off (by intestinal bacteria metabolism) and then the dirheinanthrone molecule (also known as Sennidin) passively separates.

Sennosides may passively degrade into glycosides of rhein anthrones, called 8-glucosyl rhein anthrones, but usually passively reform before being metabolized by bacteria and moving rightwards in the diagram below.

1.3. Properties

Sennosides are insoluble in water, and barely soluble in methanol; however, an aqueous mixture of 30% water and 70% methanol can dissolve Sennosides. Sennosides are also soluble in sodium bicarbonate as it neutralizes their acidity.[10][4]

It is possible that Sennosides can be degraded into rhein anthrone molecules during shelf-life,[11] and it is recommended to avoid all moisture and heat in storage of Senna plants, extract, or pills/capsules.[1]


2.1. Metabolism

The anthranoid class of molecules are resistant to acid digestion in the stomach as well as enzymatic digestion by the small intestine due to possessing a beta-glycosidic bond, typical of dietary fibers.[12] Due to an inability to be metabolized and absorbed, they are then sent to the large intestines (colon) where colonic bacteria (of the Bifidobacterium class)[13][14] can hydrolyze the bond and release free rhein anthrone, which is bioactive in the colon.[12][15] In this sense, the rhein anthrone is seen as the active component whereas the Sennosides are seen as pro-drugs.[12]

2.2. Systemic

Although Senna should not reach systemic circulation by the above mechanisms, a small amount of rhein has been reported in the breast milk of mothers after oral Senna usage (although insufficient to cause laxative effects in the infant fed).[1]

3Interactions with the Colon

3.1. Laxatative Effects

There are two mechanisms by which Senna products (and the anthranoid class of laxatives) exerts pro-motility effects. Altering intestinal contractions to favor peristalsis while inhibiting location contractions (in and of itself a pro-motility effect) and inducing secretion of electrolytes into the colon and limiting liquid absorption to increase colonic water content and exert stool softening effects.[16][17]

4Safety and Toxicity

4.1. General

In studies on rats, senna appears to exert little toxicity.[18][19] The LD50 has been implicated at around 5,000mg/kg bodyweight in both rats and mice, and is possibly secondary to electrolytic imbalance from the colon.[20][21]

In regards to genotoxicity and mutagenicity, they appear to exert weak effects.[22][23][24]

When looking at the causative molecules, it appears that the main laxative components Sennoside A and B exert minimal toxicity while lesser molecules (such as rhein-8-glucoside) exert more toxicity relative to the Sennosides.[18][21]

The emodin molecules, Aloe-Emodin and Emodin, have been shown in one study to have genotoxic effects[25] while exerting no genotoxicity in another.[26]

4.2. In vivo testing

A rat study using 1% dietary anthranoid (hidroxyanthraquinones) intake for 480 days, a large intake coupled with prolonged dietary period, induction of bowel tumors was noted.[27] Lower doses (50-300mg/kg bodyweight whole extract) over 2 years does not cause carcinogenic effects, but may cause some reversible abnormalities such as benign colonic hyperplasia in rats[28] which is not seen in clinically relevant doses of 5-25mg/kg bodyweight over 2 years in rats.[29]

In humans, an association was found in the past between laxatives of this class (the anthranoid laxatives)[30] but is contested.[31] No causation has been established between chronic use of Senna products and colorectal cancer risk in humans.

The above toxicological reports suggest that Senna usage is fine if not abused (in dose) and kept relatively short, with normal doses over a prolonged period having the ability to cause some reversible abnormalities. Large doses of senna for chronic periods of time may be a risk factor for colon cancer and has biological plausibility, but has not been fully demonstrated yet

Scientific Support & Reference Citations


  1. WHO: Fructus Sennae Document
  2. New and Noteworthy Cassias from Tropical Africa
  3. Li H, et al Analysis on changes of purgative biopotency in different processed products of rhubarb . Zhongguo Zhong Yao Za Zhi. (2012)
  4. Yamasaki K, et al Simple and rapid analysis of sennoside A and sennoside B contained in crude drugs and crude drug products by solid-phase extraction and high-performance liquid chromatography . J Nat Med. (2010)
  5. Hayashi S, et al Analytical studies on the active constituents in crude drugs. IV. Determination of sennosides in senna and formulations by high-performance liquid chromatography . Chem Pharm Bull (Tokyo). (1980)
  6. Bala S, et al An improved method for the analysis of sennosides in Cassia angustifolia by high-performance liquid chromatography . Phytochem Anal. (2001)
  7. Mena-Rejón GJ, et al Racemochrysone, a dihydroanthracenone from Senna racemosa . Z Naturforsch C. (2002)
  8. Terreaux C, et al Complete LC/MS analysis of a Tinnevelli senna pod extract and subsequent isolation and identification of two new benzophenone glucosides . Planta Med. (2002)
  9. Franz G The senna drug and its chemistry . Pharmacology. (1993)
  10. The Merck Index: 14th edition
  11. Goppel M, Franz G Stability control of senna leaves and senna extracts . Planta Med. (2004)
  12. Lemli J Metabolism of sennosides--an overview . Pharmacology. (1988)
  13. Matsumoto M, et al Promotion of intestinal peristalsis by Bifidobacterium spp. capable of hydrolysing sennosides in mice . PLoS One. (2012)
  14. Akao T, et al Isolation of a human intestinal anaerobe, Bifidobacterium sp. strain SEN, capable of hydrolyzing sennosides to sennidins . Appl Environ Microbiol. (1994)
  15. de Witte P Metabolism and pharmacokinetics of anthranoids . Pharmacology. (1993)
  16. Ewe K, Ueberschaer B, Press AG Influence of senna, fibre, and fibre + senna on colonic transit in loperamide-induced constipation . Pharmacology. (1993)
  17. Godding EW Laxatives and the special role of senna . Pharmacology. (1988)
  18. Hietala P, et al Laxative potency and acute toxicity of some anthraquinone derivatives, senna extracts and fractions of senna extracts . Pharmacol Toxicol. (1987)
  19. Mengs U, et al A 13-week oral toxicity study of senna in the rat with an 8-week recovery period . Arch Toxicol. (2004)
  20. Hallmann F Toxicity of commonly used laxatives . Med Sci Monit. (2000)
  21. Morales MA, et al Is senna laxative use associated to cathartic colon, genotoxicity, or carcinogenicity . J Toxicol. (2009)
  22. Mukhopadhyay MJ, et al Genotoxicity of sennosides on the bone marrow cells of mice . Food Chem Toxicol. (1998)
  23. Mereto E, Ghia M, Brambilla G Evaluation of the potential carcinogenic activity of Senna and Cascara glycosides for the rat colon . Cancer Lett. (1996)
  24. Sandnes D, et al Mutagenicity of crude senna and senna glycosides in Salmonella typhimurium . Pharmacol Toxicol. (1992)
  25. Westendorf J, et al Genotoxicity of naturally occurring hydroxyanthraquinones . Mutat Res. (1990)
  26. Heidemann A, Miltenburger HG, Mengs U The genotoxicity status of senna . Pharmacology. (1993)
  27. Mori H, et al Carcinogenicity of naturally occurring 1-hydroxyanthraquinone in rats: induction of large bowel, liver and stomach neoplasms . Carcinogenesis. (1990)
  28. Mitchell JM, et al An oral carcinogenicity and toxicity study of senna (Tinnevelly senna fruits) in the rat . Arch Toxicol. (2006)
  29. Lydén-Sokolowski A, Nilsson A, Sjöberg P Two-year carcinogenicity study with sennosides in the rat: emphasis on gastro-intestinal alterations . Pharmacology. (1993)
  30. Anthranoid laxative abuse--a risk for colorectal cancer?
  31. Kune GA Laxative use not a risk for colorectal cancer: data from the Melbourne Colorectal Cancer Study . Z Gastroenterol. (1993)
  32. Patel M, et al The use of senna with docusate for postoperative constipation after pelvic reconstructive surgery: a randomized, double-blind, placebo-controlled trial . Am J Obstet Gynecol. (2010)
  33. Amato A, et al Half doses of PEG-ES and senna vs. high-dose senna for bowel cleansing before colonoscopy: a randomized, investigator-blinded trial . Am J Gastroenterol. (2010)
  34. Kositchaiwat S, et al Comparative study of two bowel preparation regimens for colonoscopy: senna tablets vs sodium phosphate solution . World J Gastroenterol. (2006)
  35. De Salvo L, et al The bowel cleansing for colonoscopy. A randomized trial comparing three methods . Ann Ital Chir. (2006)
  36. Valverde A, et al Senna vs polyethylene glycol for mechanical preparation the evening before elective colonic or rectal resection: a multicenter controlled trial. French Association for Surgical Research . Arch Surg. (1999)
  37. Agra Y, et al Efficacy of senna versus lactulose in terminal cancer patients treated with opioids . J Pain Symptom Manage. (1998)
  38. Kinnunen O, et al Safety and efficacy of a bulk laxative containing senna versus lactulose in the treatment of chronic constipation in geriatric patients . Pharmacology. (1993)
  39. Shelton MG Standardized senna in the management of constipation in the puerperium: A clinical trial . S Afr Med J. (1980)
  40. Rogers HJ, et al Comparison of the effect of drugs upon some commonly used measures of bowel transit time . Br J Clin Pharmacol. (1978)
  41. Sykes NP A volunteer model for the comparison of laxatives in opioid-related constipation . J Pain Symptom Manage. (1996)

(Common misspellings for Senna alexandrina include Sena, cena, cenna, alexandria)

(Editors who contributed to this page include , )