bivores or pathogens but also decrease the chances of these organisms developing resistance or adaptive
responses [7–9].
IV. PROPERTIES, USES, AND PHYTOMEDICINAL CHEMICALS OF
SEVERAL FREQUENTLY USED MEDICINAL PLANTSAlthough thousands of medicinal plants are utilized in Western and non-Western medical approaches, a
relatively small number have received considerable use and interest in the United States over the past
decade (see Ref. 4). As shown in Table 1, nine medicinal plants represented about 80% of the total mar-
ket for U.S. sales of medicinal plant products in 1999 [10]. The sales for each of these plants increased
over the previous year, although with a wide range in the extent of increase. In 1999, sales of kava, saw
palmetto, St. John’s wort, and ginseng demonstrated the largest increase over the previous year [10], and
this probably reflects both increased visibility for these medicinal plants in the popular media (and com-
mercial advertisement) and recognition of their effectiveness. The data shown in Table 1 are for 1999
sales, but it should be noted that interest in these nine particular medicinal plants remained constant over
at least the previous 5 years. The plants shown in Table 1 have remained within the top 10–15 plants dom-
inating medicinal plant sales, although the percentage of the market and relative increase have varied from
year to year [4]. What follows is an overview of these nine plants that have dominated medicinal plant
use and interest in the United States, focusing on their biochemical characteristics and the pharmacolog-
ical actions of their plant secondary product chemicals.
A. Ginkgo
Ginkgo bilobais the last living relative of a primative family of gymnosperms (Ginkgoaseae); all other
species exist only as fossils [11,12]. Ginkgo trees are widely used as ornamentals worldwide because of
their hardiness and appearance. The therapeutic use of G. bilobadates back about 2000 years in traditional
Chinese medicine [11,13]. On the other hand, the phytomedicine utilized today is based on acetone ex-
traction of the fan-shaped leaves and further purification of active constituents [14–16]. Clinical studies
have supported the effectiveness of G. bilobain improving peripheral and cerebrovascular circulation
[11,13,16–19]. A main use of G. bilobais in the management of cognitive decline associated with dis-
turbances in brain blood circulation (i.e., vascular insufficiency dementia) that can occur in the elderly
(Refs. 15, 17, and 18 and references therein). In addition, G. bilobaextracts have been useful in the treat-
ment of tinnitus and vertigo and for improving circulation in the legs [11,15,16]. It should be noted that
the effectiveness of G. bilobaextracts in improving the cognitive performance of young healthy individ-
uals is less certain.
The active constituents present in extracts of G. bilobaleaves have been shown to be a mixture of
terpene lactones and flavonoids [11,12,16,19,20]. Most commercial preparations of G. bilobaare leaf ex-
tracts standardized to about 5 to 7% terpene lactones and 22 to 27% flavonoids [18–21]. The prominent
terpene lactones in G. bilobaextracts are ginkgolides A, B, C, J, and M and bilobalide (Figure 1). While
the ginkgolides are considered to be diterpenes and bilobalide is considered to be a sesquiterpene, the lat-
ter compound most likely represents a product of ginkgolide metabolism [11,19]. Studies by Cartayrade
et al. [22] have shown that although G. bilobaleaves represent sites of ginkgolide (and bilobalide) accu-
PHYTOMEDICINAL CHEMICAL PRODUCTION BY PLANTS 487
TABLE 1 1999 Sales of Medicinal Plant Products in the United States
Plant % of total sales Change from 1998 (%)
Ginkgo biloba 21.0 6.0
St. John’s wort 15.9 23.2
Ginseng 12.3 15.6
Garlic 11.2 11.4
Echinacea/goldenseal 9.1 0.2
Saw palmetto 6.1 37.8
Kava 2.4 456.0
Valerian 1.2 3.2
Source: Data from Ref. 10.