1.5 Alternatives to anthelminthic
1.5.6 Botanical extracts
1.5.6.1. Mechanisms of botanical extracts
The mode of action of some botanical extracts is poorly understood. However, there are reported mechanisms for some. For example, Gillian et al. (2004) reported that plants such as Ananas comosus Merr, Carica papaya L. cv. Rathna and Ficus spp contain products that can digest the cuticle of nematode, leading to their death. The active ingredients of these plants are proteolytic enzymes of the papaya, the enzyme ficin from fig trees and cysteine proteinases of pineapples. These enzymes have been used in medicine. Papain from papaya is used as anti- inflammatory substance. Chymopapain is used to treat prolapsed intervertebral discs with a similar success rate to surgery. The enzyme ficin from Ficus spp is also used as an anti- inflammatory agent (Stepek et al., 2004). Fresh pineapple juice was found to possess an enzyme, bromelain, which is similar to ficin. Gillian et al. (2004) showed that proteolytic enzymes from the genus Ficus have anthelmintic action.
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Allium sativum Linn contains a sulphuric compound that has anthelminthic effects (Singh et al., 2009). Ferri et al. (2003) isolated another sulphuric compound from A. sativum blub called Ajoene. Ajoene inhibits protein prenylation and arterial smooth muscle cell proliferation in parasites, which would be fatal (Ferri et al., 2003).
Extracts of leaves and seeds of neem (Azadirachta indica A. Juss) trees also have anthelmintic effects in small ruminants (Thomas et al., no date; Costa et al., 2006). Akhtar (1999) reported that neem contains several chemicals (e.g. azadirachtin, nimbocinol and nimbin) which are responsible for the nematicidal properties. In vivo trial using neem leaves in goats showed 100% reduction in faecal egg counts (Radhakrishnan et al., 2007). When leaves of the neem tree were fed to parasitized sheep, no anthelmintic effect was however recorded against H.
contortus (Githiori, 2004).
Another plant-based nematode control method lies on grazing of plants containing condensed tannins (CT) (Min et al., 2003). Growing these plants for hay or grazing, to be used as a natural de-worming agent, may be a cost-effective, environmentally friendly alternative to the exclusive use of chemical anthelmintics by small ruminant producers (Shaik et al., 2004).
Generally, CT are phenolic compounds found in forage legumes, trees and stems (Barry and McNabb, 1999). Condensed tannins are widely distributed in legume pasture species such as Lotus corniculatus L. cv. Grassland Goldie and in several Acacia spp (Degen et al., 1995), and Lespedeza cuneata Dum.Cours (Min et al., 2004). Condensed tannins have either beneficial or detrimental effects on ruminants, that depending upon their level of intake and their structures (Min et al., 2003). Low to moderate level of CT can improve animal performance (Waghorn and Shelton, 1997; Athanasiadou et al., 2001b; Min et al., 2003). Levels of CT less than 50 mg kg-1 BW in feed can reduce the risk of bloat, increase the uptake of essential amino acids, enhance the production of milk and wool, and be effective against gastrointestinal parasites (Athanasiadou et al., 2001b). However, higher levels of CT could decrease voluntary feed intake, digestibility of fibre in the rumen and animal growth (Rojas et al., 2006).
The manner in which condensed tannins affect nematode parasites can be classified as a direct
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or an indirect effect. A direct effect of CT might be mediated through CT–nematode interactions affecting physiological functions of gastrointestinal parasites (Rochfort et al., 2008; Hoste et al., 2012). Condensed tannins can also react directly by interfering with egg hatching, and larval development to infective larval stage (Min and Hart, 2003). This reduces pasture contamination and infective larvae ingestion, which in itself might provide adequate control of gastrointestinal parasites. Condensed tannins also have the ability to bind with proteins in nematode walls, making them inactive or killing them (Athanasiadou et al., 2001a).
Non-direct effects of CT appear to be improving protein nutrition by binding to plant proteins in the rumen to prevent microbial degradation; this increases protein flow to the duodenum.
Min and Hart (2003) have shown improved protein nutrition decreases parasite infection by enhancing host immunity.
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Table 1. 3: Some botanical extracts used in vitro to control gastrointestinal nematodes in animals around the world
Plant family Plant scientific name
Country of Use
Method of Preparation
Claims References Asphodelaceae Aloe ferox South
Africa
Leaf extract Effective Maphosa et al., 2010 Liliaceae Allium sativum Pakistan Water extract
of the garlic bulb
Effective Iqbal et al., 2001
Myrsinaceae Myrsine africana
Kenya Dried fruits and leaves
Ineffective even with the highest dose
Githiori et al., 2002
Fabaceae Lespedeza
cuneata
USA Dried ground
hay
Reduction of nematodes
Min et al., 2003;
2004
Caricaceae Papaya carici Not stated Latex extract Effective Adu et al., 2009 Moraceae Ficus spp. Not stated Juice extract Effective Gillian et al., 2004 Bromeliaceae Ananas
comosus
Not stated Juice extract Effective Gillian et al., 2004 Bromeliaceae Ananas
comosus
Pakistan Philippines
Raw powder Ineffective Hördegen et al., 2003.
Zingiberaceae Zingiber officinale
Pakistan Ethanol extract of Rhizomes
Effective Iqbal et al., 2001
Meliaceae Azadirachta indica
Bangladesh Ethanol extract from leaves
Effective Sujon et al., 2008
Anacardiacae Spondias mombin
Nigeria Aqueous and ethanolic crude extract
Effective Ademola et al., 2005
19 Plant family Plant scientific
name
Country of Use
Method of Preparation
Claims References
Fabaceae Hedysarum
coronarium
Newzerland Condensed tannin extracts in aqueous solution
Effective Niezen et al., 2002.
Leguminosae Tephrosia vogelli
Ethiopia Ethanol extract of leaves
Effective Siamba et al., 2007
Fabaceae Lotus
corniculatus
USA Condensed
tannin extracts in aqueous solution
Effective Min et al., 1999
Cucurbitaceae Curcurbita mexicana
Not stated Ethanol extract of whole fruit
Effective Iqbal et al., 2001
Fabaceae Lotus
pedunculatus
USA Condensed
tannin extracts in aqueous solution
Effective Molan et al., 2000
Amaranthaceae Halothamnus somaliensis
Ethiopia Crude
preparation of roots powder
Effective Dawo and Tibbo, 2005
Leguminosae Ornobrychis viciafolia
France Aqueous
acetone extract
Effective Paolini et al., 2003
Fabaceae Caesalpinia crista
Pakistan Philippines
Aqueous ethanol extract
Ineffective Hördegen et al., 2003.
Compositae Vernonia anthelmintica
Pakistan Philippines
Raw powder Ineffective Hördegen et al., 2003.
20 Plant family Plant scientific
name
Country of Use
Method of Preparation
Claims References Lamiaceae Leonotis
leonurus
South Africa
Aqueous extract of leaves
Effective with high doses
Maphosa et al., 2010
Fabaceae Elephantorrhiza elephantina
South Africa
Aqueous extract of leaves
Effective with high doses
Maphosa et al., 2010
Fumariaceae Fumaria parviflora
Pakistan Philippines
Aqueous ethanolic extract
Ineffective Hördegen et al., 2003.
Mimosaceae Albizia anthelmintica
East Africa, Kenya, Sweden, Ethiopia, Uganda
Heat treated or soaked in water
Ineffective Minja, 1994; Desta, 1995; Grade and Longok, 2002
Fabaceae Peltophorum africanum
South Africa
Ethanol extract of dried leaves
Effective Bizimenyera, 2008
Cucurbitaceae Momordica charantia
Bangladesh Ethanol extract of dried leaves
Effective Sujon et al., 2008
Canellaceae
Fabaceae
Warburgia salutaris
Acacia karoo Acacia nilotica
South Africa Zimbabwe
Acetone extract of dried leaves dried leaves
Effective
Effective
McGaw and Eloff, 2005
Kahiya et al., 2003
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