**12. Other activities**

EOs and their monoterpenes affected bone metabolism when added to the food of rats. It was demonstrated that these lipophilic compounds inhibited bone resorption [114]. It was reported that (2*E*,6*R*)-8-hydroxy-2,6-dimethyl-2-octenoic acid, a novel monoterpene, from *Cistanche salsa* had antiosteoporotic properties [115].

Pine EOs prevented bone loss in an osteoporosis model (ovariectomized rats). The monoterpenes borneol, thymol and camphor directly inhibited osteoclast resorption [114]. It was observed that inactive monoterpenes can be metabolized to their active forms *in vivo*; thus, *cis*-verbenol, a metabolite of *α*-pinene, inhibited osteoclastic resorption activity, in contrast to the parent compound *α-*pinene.

Potential activities for the treatment of Alzheimer's disease were demonstrated in a pilot open-label study involving oral administration of the EO of *Salvia lavandulaefolia* Vahl. known as Spanish sage [7].

Chinese angelica (*Angelica sinensis*) is the most important female tonic remedy in Chinese medicine. The effects of angelica EO in three assays in mice (elevated plus maze, light/dark and stress-induced hyperthermia test) suggested that angelica EO exhibited an anxiolytic-like effect [116]. A link to emotion and cognitive performance with the olfactory system was reported [117]. Moreover, the EOs could affect mood, concentration and sleep [118], while other studies had shown that EOs were potentially important to boost the immune system [119, 120].

EOs from different *Lippia alba* chemotypes showed behavioral effects. Greater effects were presented by chemotype 2 (with citral and limonene), while chemotype 1, containing citral, myrcene and limonene, decreased only the number of rearings in the open-field test [121]. The EO of lemon was found to modulate the behavioral and neuronal responses related to nociception, pain and

**167**

*Essential Oil as Antimicrobial Agents: Efficacy, Stability, and Safety Issues for Food Application*

anxiety [122, 123]. Thus, there is widespread and increasing interest in comple-

*Aloe vera* gel enhanced the antiacne properties of *Ocimum gratissimum* L.oil; the oil or its combination with *Aloe vera* gel was more effective than 1% clindamycin in the treatment of *Acne vulgaris* [124]. Linalool-rich EO was potent against promasti-

Plant extracts have shown a considerable promise in a range of applications in the food industry and several plant extracts enjoy GRAS status. The antimicrobial activities of plant extracts may reside in a variety of different components and several extracts owing to their phytochemical constituents have been shown to have antimicrobial activity. The antibacterial activity is most likely due to the combined effects of adsorption of polyphenols to bacterial membranes with membrane disruption and subsequent leakage of cellular contents [126, 127], and the generation of hydroperoxides from polyphenols [128]. Plant extracts also showed antifungal activity against a wide range of fungi, antioxidant and antimutagenic activities [129] and inhibited lipid oxidation in foods [130]. Although numerous studies have been done *in vitro* to evaluate the antimicrobial activity of plant extracts, very few studies are available for food products, probably because plant extracts did not produce as marked inhibition as many of the pure compounds in foods. The reduced effectiveness may be attributed to the use of crude extracts in most studies. As the crude extracts generally contain flavonoids in glycosidic form, where the sugar present in them decreases effectiveness against some bacteria [131, 132]. Dietary herbs and spices have been traditionally used as food additives throughout the world not only to improve the sensory characteristics of foods but also to extend their shelf life by reducing or eliminating survival of pathogenic bacteria. Herbs and spices are rich in phenolic compounds and besides exerting antimicrobial effect they may preserve the foods by reducing lipid oxidation as they are reported to have significant antioxidant activity [133]. A wide variety of phenolic substances derived from herbs and spices possess potent bio- logical activities, which contribute to their preservative potential [134]. Careaga et al. [135] reported that 1.5 ml/100 g of capsicum ex- tract was sufficient to prevent the growth of *Salmonella typhimurium* in raw beef but that 3 ml/100 g was required for a bactericidal effect against *P. aeruginosa*. Treatment with hydrosol of thyme, black cumin, sage, rosemary and bay leaf was reported to reduce *S. typhimurium* and *E. coli* O157:H7 in apple and carrots [136]. Black cumin ethanolic extract applied in a marinade base for raw trout was found to reduce aerobic plate count, yeast, and coliforms [137]. Lee et al. [138] observed that the addition of green tea or rosemary (1 or 3%) to rice cakes significantly reduced the levels of *B. cereus* and *S. aureus* during 3 days storage at room temperature (22°C). Ahn et al. [139] reported that a range of plant extracts are useful for reduction of pathogens associated with cooked beef, however, Uhart et al. [140] reported that spices inactivate *S. typhimurium* DT104 in *in vitro* condition, but the activity decreased considerably when added to a complex food system such as ground beef. Kim et al. [141] observed that ground beef samples did not show significant difference in *L. monocytogenes*, *S. aureus* and total bacterial counts after treatment with green and jasmine tea as compare to untreated samples, however, a slight reduction in viable count of *Salmonella enterica Serotype Enteritidis* and *Listeria monocytogenes* in ground beef by watersoluble arrowroot tea extract (upto 6% w/w) was reported [142]. Combination of

*DOI: http://dx.doi.org/10.5772/intechopen.92305*

**13. Plant extracts**

mentary and alternative medicines using EOs [124].

gotes and amastigotes of *Leishmania amazonensis* [125].

*Essential Oil as Antimicrobial Agents: Efficacy, Stability, and Safety Issues for Food Application DOI: http://dx.doi.org/10.5772/intechopen.92305*

anxiety [122, 123]. Thus, there is widespread and increasing interest in complementary and alternative medicines using EOs [124].

*Aloe vera* gel enhanced the antiacne properties of *Ocimum gratissimum* L.oil; the oil or its combination with *Aloe vera* gel was more effective than 1% clindamycin in the treatment of *Acne vulgaris* [124]. Linalool-rich EO was potent against promastigotes and amastigotes of *Leishmania amazonensis* [125].
