Essential oils from aromatic and medicinal plants have been known since antiquity to possess biological activity, notably antibacterial, antifungal as well as antioxidant properties (Tiziana and Dorman, 1998). With the increasing interest in the use of essential oil in both the food and the pharmaceutical industries, a systematic evaluation of plant extracts for these properties has become increasingly important. Bacterial and fungal infections pose greater threats to health and hence the use of natural antimicrobial compounds is important in the control of human and plant diseases of microbial origin.
Yadava and Saini (1991a) studied the antimicrobial effect of marjoram and found that fungi which were inhibited are A. fumigatus and A. niger. Studies by Ueda et al. (1982)
revealed that the Minimum Inhibitory Concentration (MIC) required for fungi such as S. cerevisiae, C. paracrusei, C. krusei and A. oryzae was <4.0%. Tiziana and Dorman (1998) reported antifungal activity of marjoram oil against the common spoilage fungus Aspergillus niger (strain IMI 17454) even at concentration of 1 micro litre/ml broth.
Huhtanen (1980) observed that the MIC of hexane extract of marjoram needed for control of bacteria such as E. coli, Salmonella sp., S. aureus, B. cereus and Campylobacter was 10% while Ueda et al. (1982) reported that only a lower concentration of 4% was necessary for control of bacteria such as Bacillus subtilis, S. aureus 209P, E. coli, S. tphimurium, S. marcescens, P. aeruginosa, P. vulgaris and P. morganii at pH levels of 5 or 7. B. subtilis and S. aureus were the most vulnerable and at pH 5.0 the MIC for these two bacteria were 0.5 and 0.2% respectively. The antibacterial effect of marjoram oil was reported by many other workers (Galli et al., 1985; Deans and Ritchie, 1987; Deans and Svoboda, 1990; Yadav and Saini, 1991a). Tiziana and Dorman (1998) noticed that marjoram oil was most active in inhibiting the growth of Acinobacter calcoacetica, Beueckea natriegens and Staphylococcus aureus. However, Deans and Svoboda (1990) noticed marjoram oil to be least effective against S. aureus, which is a food poisoning bacterium.
The discovery of inhibition of lipid oxidation by some phenolic compounds during the late 1940s has contributed to the application of synthetic antioxidants in the food industry (Dapkevicius et al., 1997). Widely used artificial antioxidants such as butylated hydroxytoluene (BHT), and butylated hydroxyanisole (BHA) (Chan, 1987) are very effective in their role. However, their use in food products has been falling off due to their instability, strict legislation on the use of synthetic food additives, as well as due to a suspected action as promoters of carcinogenesis (Namiki, 1990; Pokorny, 1991; Duh and Yen, 1997). For these reasons there is a growing interest in the study of natural additives as potential antioxidants. The antioxidant properties of many herbs and spices are reported to be effective in retarding the process of lipid peroxidation in oils and fatty acids and have gained interest of many research groups. Shahidi et al. (1992) and Madsen et al. (1997) suggested that the antioxidant effect of aromatic herbs is due to the presence of hydroxy groups in their phenolic compounds. Tsimidou and Boskou (1994) concluded that among the herbs and spices extensively studied, the plants obtained from the Lamiaceae (Labiatae) family possess a significant antioxidant activity.
Some natural polyphenols have therapeutic effects or a protective action against cardiovascular diseases and some cancers (Heinonen et al., 1998) and their use as a means of increasing the shelf-life of food products, improving the stability of fats and oils rich in polyunsaturated fatty acids (PUFAs), in slowing down the ageing process and in the treatment of human diseases such as atherosclerosis and cancer was also reported (Tiziana and Dorman, 1998). They observed that in egg yolk assay, the antioxidant activity of marjoram was much higher than that of a-tocopherol and comparable with that of BHT at all concentrations tested (100 to 1000ppm).
Saito et al. (1976) have obtained a higher antioxidant activity of marjoram at 0.02% against lard than tocopherol. Similar reports of effectiveness of marjoram as an antioxidant are available from other workers (Dapkevicius et al., 1997; Trombetta et al., 1998). Biacs and Wissgott (1997) noticed that ground tomato seeds with rosemary and marjoram stabilized the carotenoid pigments by way of their antioxidizing power. El-Alim et al. (1999) studied the effect of different dried spices and noticed that utilization of spices such as marjoram, wild marjoram and caraway and their mixtures or extracts in semi-prepared meat products intended to be frozen for up to six months or more before consumption is proved to be advantageous in regard to shelf-life of the food as well as for human health.
Even though many workers noticed favourable antioxidant effect of marjoram as described above, Baardseth (1989) could not replace the antioxidant BHA in potato flakes production if stored for up to 24 months by others like TBHQ, a-tocopherol, Prolong P (rosemary, thyme, marjoram mixture) or ascorbyl palmitate. Economou et al. (1991) found that marjoram extract was much less effective as an antioxidant than rosemary or oregano extract.
Okazaki et al. (1998) investigated the inhibitory effect of methanol extracts of 20 herbal species on human platelet aggregation, a factor in conditions such as thrombosis. Allspice, basil, marjoram, tarragon and thyme strongly inhibited the platelet aggregation induced by collagen. Basil, marjoram and tarragon strongly inhibited platelet aggregation induced by ADP. They isolated an active compound, arbutin, from sweet marjoram as an inhibitor of platelet aggregation.
Yamazaki (1995) studied the effect of both medicinal and edible herbs and plants of the Labaiatae family including marjoram against HIV. Though he found non-inhibitory action on HIV for 70% ethanol extract of marjoram, at a concentration of 31 ^g/ml of water extract showed effects of inhibition of HIV-1 on Molt 4 (MT-4) cells. Formation of giant cell was also found to be inhibited by concentration of marjoram extract at 125 ^g/ ml. He suggested that the mechanism of their anti-HIV activity is due mainly to their inhibitory action on cell-to-cell adsorption.
Pruthi (1976) reported that intravenous injection of dogs with a saturated solution of essential oil in 33% ethyl alcohol (1 cc/kg body weight) increased peristaltic movement of intestine. Studies by Krukowski et al. (1998) in Poland have shown that mineral herbal supplements including nettle, St. John's wort, camomile, salvia, agrimony and marjoram tended to increase the immunoglobulin G (IgG) serum level of reared calves.
Herbal medicines are being used by about 80% of the world population for primary health care and particularly in the developing countries. These drugs are popular for their safety, efficacy, and cultural acceptability as well as fewer side effects, and they cure age-related diseases for which modern medicines have not been completely successful. Ghos (2000) estimated that the herbal medicine market in Europe and America is worth ten and four billion US$ respectively.
Use of marjoram in medicinal preparations was in vogue from many years back. Chopra et al. (1956) reported the use of marjoram oil in hot fomentations, for acute diarrhoea, and as an expectorant. Parry (1969) described marjoram to have properties of antiseptic, antispasmodic, carminative, stimulant, expectorant and nerve tonic. It functions as cure for asthma, coughs, indigestion, rheumatism, toothache and heart conditions. According to Mabey (1988) marjoram contains tonic and astringent bitter principles, which rouse the appetite and hence it is helpful for invalids.
The leaves and seeds of marjoram are considered as astringent and a remedy for colic (Dayal and Purohit, 1971). Chiej (1984) reported that the powder acts as a sternulatory (inducing sneezing) if inhaled, and is, therefore effective against head colds. Prakash (1990) mentioned the use of volatile oil as an aromatic stimulant in colic, dyspepsia, flatulence and dysmenorrhoea.
Sweet marjoram appears to have a stronger effect on the nervous system than its wild cousin (Balz, 1999; Chevallier, 1996). Sweet marjoram is a good general tonic, helping to relieve anxiety, headaches and insomnia. The herb is also thought to reduce sexual desire (Mahindru, 1994). Junemann (1997) mentioned that marjoram oil relaxes and alleviates tension, both mental and physical, and is used in natural healing for many complaints accompanying or caused by tension. Guba Ron (2000) reported that essential oil of marjoram has menstrual-regulating or hormone-like effects.
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