BIOENSAYO III: EVOLUCIÓN DE LA INFECCIÓN

Other laxative herbs in this category that are encountered with some fre- quency are discussed next.

Aloe (aloes)

Also official in the USP XXII, the drug consists of the dried latex of several species of aloe, especially A. barbadensis Mill. (A. vera L.), known in com- merce as Curaçao aloe, or of A. ferox Mill., and hybrids of these species with

A. africana Mill. and A. spicata Bak., known in commerce as Cape aloe. All of these species are members of the family Liliaceae. The anthraquinone glycosides aloin A and B (formerly designated barbaloin) render aloe an extremely potent laxative. Although still widely used abroad, its use in the United States has declined in recent years, rendering it of relatively minor therapeutic significance.

Aloe is obtained from specialized cells, known as pericyclic tubules, that occur at the border of the outer and inner cortical layers of the meso- phyll, located just beneath the epidermis of the leaves of the aloe plant. The bitter yellow latex found there is drained and dried to a reddish black glistening mass. This drug is totally different from the colorless mucilagi- nous gel (aloe gel or aloe vera gel) obtained from the parenchyma tissue making up the central portion of the aloe leaf. Aloe gel is primarily a wound-healing agent and is discussed in Chapter 10; it should never be confused with aloe, the laxative.

Rhubarb

This consists of the dried rhizome and root of Rheum officinale Baill., R.

palmatum L., related species, hybrids grown in China (Chinese rhubarb) and Japan (R. palmatum x R. coreanum Nakai, Japanese rhubarb), or R. emodi Wall or R. webbianum Royle, native to India, Pakistan, or Nepal (Indian rhubarb). It is not common garden rhubarb, R. x cultorum Hort. (R. rhapon-

ticum Willd.), which is relatively inactive.

As is the case with aloe, this laxative herb is much more potent than cascara or senna. Its use almost always causes intestinal griping or colic. For this reason, rhubarb is seldom employed as a laxative today and can- not be considered an herb of choice. A very popular “tonic” preparation, widely sold in Europe and occasionally marketed in the United States, is Swedish bitters. Its active constituents include senna, aloe, and rhubarb; frequent use is not recommended.49

There are many other laxative herbs. Some, such as colocynth, jalap, and podophyllum, are drastic purgatives; others, such as dandelion root and manna, are so mild as to be uncertain in their action. None provides any advantage over psyllium seed, cascara, buckthorn bark, or senna.

Diarrhea

Diarrhea is characterized by increased fluidity and volume of the stool due to the excretion of a relatively large volume of water normally reab- sorbed from the gut and almost always accompanied by increased fre- quency of bowel movement. Although normal functioning of the bowels varies greatly in different individuals, which must be taken into account in the definition, diarrhea ordinarily involves defecation more than three times daily. The condition may be acute or chronic, and the causes are numerous, ranging from allergies to viral infections.

Acute diarrhea is characterized by a sudden onset of self-limited episodes of less than forty-eight hours’ duration; if it persists for more than three to four days, a physician should be consulted. It can usually be attributed to intestinal infection caused by various organisms such as

Salmonella, invasive Escherichia coli, or enterovirus. Some organisms, such as Staphylococcus aureus and toxigenic strains of E. coli, cause diarrhea through food contaminated with an enterotoxin (food poisoning). Food- induced diarrhea may also be caused by food allergy or by ingestion of foods that are excessively spicy or high in roughage. In addition, certain drugs may induce diarrhea as an adverse effect.

Chronic diarrhea is characterized by loose stools over a prolonged period, and it may be a symptom of a serious disorder of the gastrointesti- nal tract. Individuals who experience persistent or recurrent diarrhea for more than two weeks and are unaware of the cause should seek prompt medical attention from a physician.

Several preparations available as OTC drugs are effective in the treat- ment of diarrhea. These include loperamide (Imodium), bismuth subsali- cylate (Pepto-Bismol), and kaolin pectin suspension (Kaopectate). Herbal remedies are also available and are effective due to their content of poly- phenolic substances, popularly known as tannins.

These compounds tend to arrest diarrhea by their astringent action, which reduces intestinal inflammation. They effect this by binding to the surface protein layer of the inflamed mucous membranes, causing it to thicken and thereby hindering resorption of toxic materials and restricting secretions. Tannins that are slowly released from the various complexes in which they exist in the plant after reaching the lower gastrointestinal tract are most effective.50 _{This prevents stomach upset and also allows the}

tannin to act at the site where it is most effective. The most widely used astringent herbs are obtained from several edible berry plants.

Because of their similarities, the leaves of three plants may be consid- ered as a group:

blackberry leaves—the dried leaf of

• Rubus fruticosus L. (family Rosaceae);

blueberry leaves—the dried leaf of

• Vaccinium corymbosum L. or V.

myrtillus L. (family Ericaceae); and raspberry leaves—the dried leaf of

• Rubus idaeus L. or of R. strigosus Michx. (family Rosaceae).

All of the leaves contain appreciable amounts of tannin; quantities up to 6.7 percent have been reported for blueberry leaves51 _{and a range of 8}

to possibly 14 percent has been reported for blackberry leaves.52 _{All three}

are consumed in the form of teas, usually prepared by pouring a cup of boiling water over 1–2 teaspoons of the finely cut leaves and steeping for ten to fifteen minutes. Alternatively, the plant material may be macerated in cold water for about two hours and then strained to yield the beverage. A cup of the tea may be drunk up to six times a day as necessary to control the diarrhea. However, if the condition lasts more than two or three days, it is obviously not amenable to treatment with astringent herbs. The teas from all three berry leaves may also be used effectively as a mouthwash or gargle for sore mouth and inflammation of the mucous membranes of the throat.

Raspberry leaf tea has a persistent traditional reputation of utility in treating a wide variety of female conditions ranging from diabetes and menstrual difficulties to those associated with pregnancy, such as morn- ing sickness and labor pains. One reputable scientific reference continues to note that the tea has been a traditional remedy for “painful and profuse menstruation and for use before and during confinement.”53 _{The German}

Commission E concluded that the leaf has not been proven effective for any of these complaints54 _{(see Chapter 8 for additional details). Other use-}

ful antidiarrheal herbs are discussed next.