Spring Cleaning? What About Intestinal Parasites? Spring is traditionally a time for cleaning. This was well-recognized by European herbalists who used a number of herbs as "spring tonics" or "spring cleansers." Many of these spring tonics provided much needed vitamins after a lengthy period of consuming stored foods. But they also included the depurative herbs (herbs which clean the blood by unknown mechanisms) and herbs for promoting digestion, including the bitter herbs wormwood and gentian. Wormwood, as the name implies, was also traditionally used to treat gastrointestinal worm infestation. So it could be that this aspect was also part of the use of spring tonics.
Whether this is the case or not, it is true to say that the plant world has long provided options to assist in the control of intestinal parasites. A few of the more popular herbs are viewed below, together with a significant and highly active anthelmintic herb from Traditional Chinese Medicine. But the main thrust of this review is to suggest that synergistic activity via a combination of these key herbs (with other herbal treatments as well to support digestion and immunity etc.) will yield the best results.
Artemisia absinthium is well known to herbalists with particular application to treating nematode infestation, especially infestation with Enterobius or Ascaris.1,2 Wormwood has been used as an anthelmintic since ancient times and is currently utilized in many countries throughout the world for this purpose. Wormwood tincture is employed in the West Indies as a worm preventative.3 Wormwood has also been used for the de-worming of horses, cows and sheep.4,5
Constituents of the aerial parts of wormwood include bitter substances (sesquiterpene lactones, mainly absinthin) and an essential oil containing mainly terpenes. The essential oil contains the potentially toxic monoterpene thujone and for this reason the recommended therapeutic doses of wormwood should not be exceeded.6
In vitro wormwood aqueous extract demonstrated anthelmintic activity towards the nematode Trichostrongylus colubriformis.7 Thujone is also implicated in the anthelmintic activity of wormwood. Experiments carried out in Edinburgh in 1955 indicated the efficacy of thujone in eliminating Ascaris lumbricoides.8
Other Related Activity
Wormwood aqueous extract and alcohol extract strongly inhibited the in vitro growth of the parasitic protozoa Naegleria fowleri. The sesquiterpene lactone fraction isolated from the alcohol extract was also active.9
Wormwood powder (1.5 g/day) provided effective treatment for acute intestinal amebiasis in an uncontrolled trial of 20 patients. Symptoms were relieved and 70% of cases were cleared of the protozoa Entamoeba histolytica according to stool analysis.10
Wormwood is also used to treat other gastrointestinal conditions such as appetite loss, disturbed digestion, flatulence and disordered bile flow.11 Clinical trials have demonstrated the ability of wormwood to increase the flow of gastric enzymes, pancreatic enzymes and bile.12,13
Black Walnut Hulls
A globular fruit is produced from the black walnut tree which contains a corrugated nut in its yellowish-green hull (also called husk or fruit wall). Upon ripening the hull softens and turns dark brown to black due to chemical oxidation. A decoction of the hull of Juglans nigra fruit has been used traditionally to expel worms.2
The unripe hulls of Juglans nigra contain 1,4-naphthoquinones including juglone and plumbagin.14 The juglone content in hulls varies with different cultivars and different months of growth.15
In vitro studies indicate that plumbagin inhibited the motility of and hatching of Haemonchus contortus first stage larvae. Plumbagin was larvacidal towards Ascaris suum at the highest test concentration (100 mM). Partial inhibition of embryonic development of A. suum occurred with plumbagin.16 The authors suggested that because of the relatively high doses required for the maximal effect on inhibiting the development of larval stages, plumbagin may not find practical application. The combination with other anthelmintic herbs would however, boost the activity of plumbagin.
Radix Stemona, the tuberous root of Stemona sessilifolia, Stemona tuberosa or Stemona japonica, is used in Traditional Chinese Medicine (TCM) mainly for the treatment of acute and chronic cough. Externally it is used for the treatment of fungal infections, lice infestation and as an enema for pinworm infestation.17-19 In addition to its primary use for the treatment of cough, in Vietnam Stemona japonica root is prescribed for Ascaris infestation and is used externally to treat scabies (mite infestation).20
A series of complex alkaloids have been isolated from the root of these Stemona species.21The unusual and complex alkaloids exist only in Stemona plants and in a few related species and include tuberostemonine and stemonine.22
Tuberostemonine, an alkaloid isolated from Stemona sessilifolia, S. tuberosa and S. japonica root,21 paralyzed the motility of Angiostrongylus cantonensis in vitro and showed contractive effects on the motility of Dipylidium caninum and Fasciola hepatica. The experimental anthelmintic activity of crude extract of Stemona may be due to the action of tuberostemonine23 and related alkaloids.
One hundred and forty cases of ancylostomiasis (hook worm infestation) were treated with the herb. After 3 months, follow-up examination of 110 cases revealed a negative rate of 94.5%. Another group of 48 cases was effectively treated with the herb decoction; 116 worms, all from the duodenum, were expelled. However, the same method did not show any anthelmintic effects in later trials.24Alcoholic extracts will probably work better than decoction.
The suppository prepared from the herb was used to treat 40 children with oxyuriasis (infestation with a type of nematode); 16 of them were cured. Twenty-seven out of 63 cases were cured by the herb powder. Dosage: Suppository — (12.5 g each). One suppository was inserted into the rectum at 8 pm, another at 10 pm every night for one week, then every other night for another week. Powder — 1.5 g 3 times daily for 3 days.24
Clove Bud Essential Oil
The dried, unopened flower bud of Syzygium aromaticum has been used in Ayurveda and Western herbal medicine as a carminative and aromatic.2,25 It has recently been popularized as a worm treatment. Therapeutic indications for clove bud include nausea, flatulence, dyspepsia and to assist the action of other herbal remedies.2,25,26
In traditional Thai medicine the essential oil is used as a carminative and to treat stomach ache, in addition to the well-known topical application of toothache.27 In Indonesian traditional medicine clove oil is taken with beer to protect against abdominal pain! Clove bud is also used in this traditional system to alleviate flatulence.28
Key constituents of clove bud include an essential oil (15-20%, consisting mainly of eugenol, eugenol acetate, beta-caryophyllene), flavonoids, tannins and phenolic acids.29 Eugenol is a major constituent of clove bud essential oil (80-85%).30
Clove powder demonstrated potent anthelmintic activity in vitro towards Pheretima spp. (earthworms). At this time earthworms were used as a model to investigate anthelmintic activity. Suspension of clove powder was more than 5 times more potent than a water extract of cloves and clove powder was 4.5 times more potent than powdered fresh garlic. Suspension of clove powder was 7.3 times more active than the anthelmintic drug piperazine, whereas the water extract of clove was of similar potency.31 Piperazine is an anthelmintic drug which has been used to treat pinworm and roundworm infections in humans for decades.
Both the water and methanol extracts of clove bud were strongly active in a nematocidal assay.32 The assay used the second-stage larva of the roundworm Toxocara canis, which at the time of the study was highly resistant to anthelmintic drugs. The relative movability (RM) value compares the extent of movement of the test population which has been exposed to the anthelmintic agent with the movability of the control sample. Strong activity was defined as a RM value of 0 (at which all larvae are dead). A value of 100 indicates no activity (no disabling effect on the larvae), and increasingly lower RM values approaching 0 indicate stronger activity of the extracts against the larvae.
A value of 0 was obtained for clove methanolic extract at both concentrations (1 mg/mL, 10 mg/mL) and both time frames (6 h, 24 h) and for water extract (10 mg/mL) at 24 hours. Piperazine produced a RM value of 32 for 1 mg/mL after 24 hours of incubation in the same assay and other anthelmintic drugs such as phenothiazine produced a RM value of 0 under the same conditions. Eugenol produced a RM value of 0 at 1 mg/mL at 24 h, and a value of 50 at the lower concentration of 0.1 mg/mL after the same time period. The nematocidal activity of eugenol has been confirmed in another study using the same assay.33
Clove oil killed Anisakis spp. larva in vitro.34 Eugenol also demonstrated potent anthelmintic activity towards Caenorhabditis elegans in vitro35 and Rhabditis macrocerca and Ascaris suum in vitro and in vivo in mice (route unknown).36
Potential for Synergistic Anthelmintic Activity
The phenomenon known as bursting of worm larvae occurs when the outer covering of the larva is torn, resulting in protrusion of its intestine. Nematocidal assays can discover active principles that cause the killing and/or bursting of worm larvae. A constituent that has no nematocidal activity may produce bursting when combined with a nematocidal agent.
Eugenol caused bursting of worm larvae in the Toxocara assay described above.32 The activity of eugenol on its own was relatively weak (11%) but it caused marked bursting of worms (90-91%) when combined with tannins (either condensed or hydrolyzable (tannic acid)). Tannins are not larvicidal by themselves, but they cause bursting when combined with a larvacidal compound, as has been demonstrated in the same assay previously.37 In order to cause bursting, coexistence of both the anthelmintic compound and the bursting factor is necessary. The bursting activity of tannins (when combined with the suitable larvacidal substance) increased with increasing degree of condensation for condensed tannins and with increasing proportion of phenolic groups for hydrolyzable tannins.
From similar nematocidal studies investigating other essential oil components it was concluded that eugenol in combination with tannins can, even at lower concentration than its MLC (minimum lethal concentration), cause the bursting of worms if a large amount of (another) nematocidal constituent is present. (MLC was defined as the lowest concentration producing a RM value of 0 after 24 hours incubation, determined for eugenol as 0.33 mg/mL.)32
Conclusions from this and other studies by the same research team indicate that:
• a balance between the hydrophilicity (water-soluble) and hydrophobicity (fat-soluble) of the constituents is important for the larvacidal activity;38
• the bursting activity may be caused not only by tannins but also by other nonvolatile32 and volatile constituents;33
• a different bursting feature was observed for the tannin-nematocide mixture compared to the bursting caused by essential oil alone33 suggesting a different mechanism of action;
• the synergistic action of tannins and an anthelmintic not only damages the worms irreversibly, but also, in some instances markedly reduced the required amount of the anthelmintic.37
This research suggests the value of combining various herbal agents for a synergistic anthelmintic activity. It also implies that combination of anthelmintic herbs with tannin-containing herbs such as green tea and particularly herbs containing condensed tannins such as grape seed extract will enhance their activity.
Recent Anthelmintic Research
In vitro tests conducted at a government laboratory in Brisbane in 2002 using a number of herbal extracts and essential oils have indicated that clove bud and Stemona have definite positive anthelmintic activity towards a sheep intestinal nematode prevalent in this locality.39
The testing included egg hatch assay, larval development assay and infective larvae assay. At the tested dosage clove bud gave a convincing kill of the larvae population, rather than just immobilization. A field trial testing a number of herbs and essential oils for the treatment of worm infestation in sheep is pending.
Suggested Combinations for Increased Activity
The following treatments would combine well and provide synergistic anthelmintic activity with the wormwood, black walnut hulls, Stemona and clove bud essential oil mentioned above:
• tannin-containing herbs, especially preparations containing green tea (Camellia sinensis) and grape seed (Vitis vinifera) extract. These herbs should be taken concomitantly with the anthelmintic herbs.
• holy basil (Ocimum sanctum) essential oil, since the leaf has been used in traditional Ayurvedic medicine as an anthelmintic and the essential oil has demonstrated potent anthelmintic activity in vitro towards Caenorhabditis elegans.35 In the worm bursting assay outlined above32 methyleugenol demonstrated nematocidal activity but was devoid of worm bursting activity. The presence of even a small amount of eugenol (5-10%) in the methyleugenol-tannin mixture caused the bursting of the worms, particularly when the tannin as of the condensed type.32 Both eugenol and methyleugenol occur in holy basil essential oil; the amount of each varies depending upon the chemotype.40
• immune enhancing herbs such as Echinacea, and also preparations containing Andrographis paniculata and holy basil essential oil: to enhance the body's natural immune function and assist in the immune response to worm infestation. Eosinophilia (increased number of eosinophils in the blood) and elevated serum IgE (gamma-E globulin) levels are features of many helminthic infections.)
• garlic (Allium sativum) has been used as an anthelmintic in western herbal medicine,1 for example, as a decoction or freshly mashed and administered to children on an empty stomach.41 Garlic extract was effective against Rhabditis spp. and the eggs of Ascaris suum in vitro.42 In the Toxocara assay described above methanol extract of garlic (10 mg/mL) produced a RM value of 0 after 24 hours of incubation.32
• laxative herbs: to promote elimination of the worm infestation (or worm debris) via the bowel including preparations containing cascara (Rhamnus purshiana) and yellow dock (Rumex crispus).
• bitter herbs: to promote the gastric acid barrier to resist reinfestation. I recommend gentian (Gentiana lutea) liquid extract.
• digestive enzyme preparations, such as the latex of Ficus spp. which contains ficin has been used traditionally in neotropical areas such as the Amazon as an anthelmintic.43 However, concomitant intake of digestive enzymes with tannins may result in the inactivation of the enzymes.
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Phytotherapy Review & Commentary
by Kerry Bone, FNIMH, FNHAA
P.O. Box 713 • Warwick QLD 4370, Australia
+61 7 4661 0700 • Fax +61 7 46610788 • www.mediherb.com
FNIMH = Fellow, National Institute of Medical Herbalists (UK)
FNHAA = Fellow, National Herbalists Association of Australia
The contribution of Michelle Morgan in the preparation of this article is gratefully acknowledged.