Original articleCommon herbs, essential oils, and monoterpenes potently modulate bone metabolism
Introduction
Recent epidemiological data have revealed that the consumption of fruit and vegetables is associated with greater bone mineral density (BMD) in humans [1], [2]. We have previously shown that some common vegetables, salads, and herbs, which are part of the normal human diet, inhibit bone resorption in the rat [3]. In further studies, an extract made from onions with water or with ethanol/water inhibited osteoclastic resorption in vitro [4] and prevented bone loss in an osteoporosis model [5], suggesting that some constituent of onion has bone resorption inhibitory activity. Thus, our results may explain the epidemiological evidence outlined above. Others, however, claim that the effect of fruits and vegetables on bone is due to their base excess buffering metabolic acid thought to dissolve bone [1], [2]. Recently we have demonstrated in the rat that, although the inhibitory effect of vegetables, salads, and herbs on bone resorption correlates with their base excess, the two phenomena are independent. Onion and a mixture of vegetables, salads, and herbs retain their inhibitory activity on bone resorption when metabolic acid is completely buffered with potassium citrate [6]. This strongly supports our hypothesis that compounds in vegetables, salads, and herbs directly inhibit bone resorption.
During our survey of herbs looking for activity on bone metabolism, we found that sage strongly inhibits bone resorption. Sage is an herb rich in essential oil. “Essential oils are a class of volatile oils obtained from plants, possessing the odor and other characteristic properties of the plant” [7]. Monoterpenes, the major components of essential oils, belong to the group of isoprenoids containing 10 C-atoms (see Fig. 1). As the monoterpenes from the essential oil of sage inhibit sweat production [8] the consumption of an herbal tea made from sage is recommended to women suffering from hot flashes [9]. Monoterpenes are widely distributed in the plant kingdom and are present in some herbs commonly used in human nutrition. As essential oils and monoterpenes have a pleasant odor and taste when used at low concentration, they have been extracted since ancient times also from many plants, both edible and inedible, and are used today as food additives. For example, the per capita consumption of menthol in foods in the United States has been estimated to be 0.1 mg/kg/day [10]. As essential oils and monoterpenes are lipophilic compounds, they readily cross cell membranes and are therefore absorbed through the skin [11] and the lung [12]. There is therefore a long history of use of essential oils and monoterpenes for many medical applications in ointments, balms, and bath additives to be used in the relief of head and chest colds as well as muscle pain.
As we found that the essential oil from sage strongly inhibits bone resorption in the rat, we investigated several herbs rich in essential oils and various essential oils and their monoterpene components on bone metabolism, demonstrating that many of these compounds inhibit resorption in vivo and in vitro and that pine oil prevents bone loss in an osteoporosis model.
Section snippets
Processing of herbs
The locally grown herbs sage, rosemary, and thyme were carefully washed with tap water and air-dried and the leaves were ground to a fine powder.
Essential oils
Oil of cumin (Oleum carvi, rect.), oil of eucalyptus (Oleum eucalypti, >80% Ph. Eur.), oil of fennel (Oleum foeniculi), oil of juniper berries (Oleum juniperi e baccis, purum), pine oil (oil of fir, Oleum pini sibiricum), dwarf-pine oil (Oleum pini pumilionis), oil of rosemary (Oleum rosmarini, DAB), and sage oil (Oleum salviae, Dalmatian) were
Effect of herbs, essential oils and monoterpenes on bone resorption
When 1 g of powdered leaves from sage, rosemary, and thyme, herbs rich in essential oils, were fed to rats, bone resorption was inhibited (Fig. 2, lanes 1, 15, and 16).
The essential oils extracted from sage and rosemary also inhibit bone resorption (lanes 3 and 31), as do pine oil, dwarf-pine oil, the related medicinal turpentine, oil of juniper, and oil of eucalyptus (lanes 17, 18, 29, 14, and 30). Sage oil, pine oil, and turpentine inhibit bone resorption in a dose-dependent fashion (lanes
Discussion
These studies demonstrate that essential oils and their monoterpene components affect bone metabolism when added to the food of rats. Our results, using an extensively validated model that is sensitive to various inhibitors of bone resorption used clinically [3], [13], [14], [15], [16], show that these lipophilic compounds inhibit bone resorption. It has been shown that a novel monoterpene isolated from a Chinese medicinal plant has anti-osteoporotic properties [30]. However, the present
Acknowledgements
We thank P. Aeby for skillful technical assistance, Dr. C. Lim-Taylor for correcting the typescript, and G. Mühlbauer for the literature retrieval. This investigation was supported in part by the Swiss National Science Foundation (Grant 32-65329).
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