Phenolic diterpenes

Bicchi, C., Binello, A., and Rubiolo, P. 2000. Determination of phenolic diterpene antioxidants in Rosemary (Rosmarinus officinalis L.) with different methods of extraction and analysis. Phytochem. Anal. 11, 236-242. 

Many medicinal and food plants contain large amounts of antioxidants other than vitamin C, vitamin E, and carotenoids. The antioxidative effects are mainly due to phenolic compounds phenolic acids, flavonoids, and phenolic diterpenes. These namral antioxidants can exert considerable protection, in humans, against aging and cancer caused by free radicals, and can replace synthetic antioxidants such as butylated hydroxyanisole (BHA) and butylated hydroxytoluene (BHT), which are suspected to have toxic and carcinogenic effects on humans. 

As camosic acid is the major phenolic diterpene in rosemary, its concentration in plant material is of interest for further processing applications. Observing the formation of phenolic antioxidants in plant material during the season and evaluating the influence of climatic conditions should indicate growing conditions resulting in high phenolic diterpene concentration. 

Selection of a suitable extraction procedure can increase the concentration of phenolic diterpenes relative to the plant material. In addition, undesirable components can be removed prior to adding extracts to foods. For example, chlorophylls present in plant material may reduce the light stability of food during storage. Several extraction techniques have been patented (Nakatani et al., 1984 Aeschbach and Philippossian, 1989) using solvents with different polarity, such as petrol ether, hexane, toluene, acetone, methanol and ethanol. To obtain tailored extracts, the successive use of different solvents has been applied. 

Phenolic Diterpenes in Other Species of the Genus Salvia... 

The comparison of six commercial extracts (Figure 6.3) showed that C02 extraction results in the highest proportion of carnosic acid among the phenolic diterpenes (Schwarz and Temes, 1992b). Extraction solvents used for the extracts shown in Figure 6.3 were ethanol (extract 1) hexane and acetone (extract 2) ethanol (extract 3) methanol (extract 4) hexane, ethanol and methanol (extract 5) and super critical C02 (extract 6). 

FIGURE 6.3 The phenolic diterpene composition of commercial extracts from rosemary and sage (for extraction solvents used, see text). Data taken from Schwarz et al. (1992). 

Since the ancient times, spices have been added to different types of food to improve their flavor and to enhance their storage stability. The intake of herbs and spices is regulated by themselves by means of the flavor intensity of the essential oil. However, antioxidant extracts with high contents of phenolic diterpenes do not necessarily contain essential oils. Particularly, plant material from essential oil production for cosmetic or pharmaceutical products is an interesting side product to be used for the preparation of antioxidative extracts. However, data published by Richheimer et al. (1996) indicated that the deoiled biomass contains markedly less camosic acid than the dried, nondeoiled plant material. 

The strong antioxidant activity of plant material from rosemary and sage leaves compared to other herbs was already recognized by Chipault et al. (1952). The antioxidant properties of rosemary and sage are extensively documented and well related to the phenolic diterpenes. 

FIGURE 6.4 HPLC chromatogram of phenolic diterpenes in commercial rosemary extracts (ISO isorosmanol ROS rosmanol CAR camosic acid CA camosol DMIR dimethyl -isorosmanol and MCA 12-O-methylcamosic acid). 

Munne-Bosch, S., Alegre, L. and Schwarz, K. 2000. The formation of phenolic diterpenes in Rosmarinus officinalis L. under Mediterranean climate. Fur. Food Res. Technol. 210 263-267. 

Richheimer, S.L., Bernart, M.W., King, G.A., Kent, M.C. and Bailey, D.T. 1996. Antioxidant activity of lipid-soluble phenolic diterpenes from rosemary. J. Am. Oil Chem. Soc. 73 507-514. 

Schwarz, K. and Temes, W. 1992a. Antioxidative constituents of Rosmarinus officinalis and Salvia officinalis I. Determination of phenolic diterpenes with antioxidative activity amongst tocochromanols using HPLC. Z. Lebensm.-unters. Forsch. 195 95-98. 

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