The family Araliaceae comprises 3 tribes differentiated by petal shape and aestivation (the arrangement of the petals in the bud). Ginseng is a member of the tribe Aralieae, the petals being broad based and somewhat imbricate in the bud (i.e. somewhat overlapping at the tip or side). A feature of the ginseng family is the species variable occurrence of secretory canals in the cortex, phloem and medulla.
Confusion of the related genera Aralia and Panax occurs in the early literature and herbaria because Joseph Pitton de Tournefort (1656-1708) had classified the genera under the common name Aralia. Panax was later correctly described as a separate genus by the eminent Swedish botanist Carl von Linné or Carolus Linnaeus (1707-1778) using the American species Panax quinquefolium as the lectotype species and its monograph appeared in Species Plantarum published in 1753. Hu (1978) stated that the genus Panax, based on Panax quinquefolium L., was characterised by "species with an underground morphogenetic point, an aerial shoot, a whorl of digitately compound leaves, serrate, double serrate, orpinnatifid-serrate leaflets, terminal umbellate inflorescence, small flowers, 5 petals, inferior ovary, and fleshy red or orange fruits containing 2-5 pyrenes".
The species of the Panax genus demonstrate a typical bicentric distribution. In North America ginseng plants can occur in a range from 70°-90° W longitude and 34° to 47° N latitude (Thompson, 1987), an area embracing the southern part of the Canadian provinces of Quebec and Ontario to the north and in the United States of America the spine of the Appalachian Mountains down to Georgia, Mississippi and Arkansas in the south and eastwards to the edges of the Great Plains. In eastern Asia the range extends from 85° to 140° E longitude to 22° to 48° N latitude (Thompson, 1987), an area including China with north east India, Nepal and Bhutan to the west, Burma, Laos and Vietnam to the south and Manchuria, Korea and Japan to the west.
Panax species can be grouped according to their rhizome and root characteristics although rhizome characteristics do vary according to the altitude at which the plants are growing. Thickened nodes and thinner internodes are observed in plants at higher elevations and at lower levels the nodes are less pronounced and the internodes thicker. Such variations have tempted some authors to define variants as new species or subspecies. The fleshy primary root may or may not be persistent and if the tap root degenerates adventitious roots may develop from the rhizome in some species. Species possessing creeping rhizomes and fibrous root systems are regarded as primitive taxa and those with an erect rhizome and fleshy root are considered as derived taxa. Such Panax species with erect rhizomes and persistent fleshy roots include P. ginseng, P. pseudoginseng, P. quinquefolium, P. trifolium, P. vietnamensis, P. wangianum and P. zingiberensis. Typical roots are pale yellowish buff in colour.
As morphological variations are not reliable criteria for the differentiation of species, considerable debate occurs concerning the true status of species and varieties. Cytogenetic study of some ginseng species has revealed that P. ginseng, P. japonicum and P. quinquefolium plants are tetraploid, i.e. the nuclei contain four times the haploid unpaired set of chromosomes. In contrast P. pseudoginseng=P. notoginseng and P. trifolium are characterised by a diploid state i.e. the nuclei contain twice the haploid unpaired set of chromosomes. Typically the somatic chromosome number for the diploid species is n=24 and for the tetraploid plants n=48 (Thompson, 1987).
Nevertheless there is still some doubt concerning the status of the wild Asiatic species or varieties and many scientific journals and particularly abstracting journals refer to P. ginseng [P. pseudoginseng] suggesting synonymy. The difficulties of differentiation by traditional macroscopical and microscopical morphological examinations prompted studies establishing the 18S ribosomal ribonucleic acid (RNA) gene sequences of extracted total deoxyribonucleic acid (DNA) from roots of P. ginseng, P. japonicus and P. quinquefolium. In 1995 Shaw and But investigated the DNA from dried and fresh roots of the three species, P. ginseng, P. notoginseng and P. quinquefolium, amplifying by the arbitrarily-primed polymerase chain and random-primed polymerase chain reactions. Resultant fingerprints of P. ginseng and P. quinquefolium proved to be consistent irrespective of source or age of the sample. As substitutes and adulterants yielded different fingerprints the method has applications for quality control. Roots of P. ginseng and P. quinquefolium were shewn to be more closely related to each other than to P. notoginseng.
DNA is formed of nucleotides, products of the combination of one molecule of phosphoric acid, one molecule of the 5-carbon sugar 2-deoxy-D-ribose and one molecule of one of the four bases adenine and guanine (purines) or thymine and cytosine (pyrimidines); the resultant nucleotides are adenylic acid, guanylic acid, thymidylic acid and cytidylic acid respectively. The DNA skeleton comprises two chains of alternate sugar and phosphate units twisted around each other in a double spiral or double helix formation with a base attached to each sugar and the two chains are held together by hydrogen bonding of the bases. DNA occurs mainly in the cell nucleus and controls the formation of the cytoplasmic nucleic acid, ribonucleic acid (RNA), by a process named transcription. RNA differs from DNA by the presence of the sugar D-ribose (C5H10O5) instead of 2-deoxy-D-ribose (C5H10O4) and the base thymine is replaced by the base uracil. As the base sequence in DNA replicates itself accurately and provides in code the genetic pattern of a particular species, the transcribed and edited RNA, which controls protein synthesis in the cytoplasm, will also be of diagnostic interest.
Therefore the 18S ribosomal RNA regions were amplified by the polymerase chain reaction to facilitate sequence determination. In each species the DNA skeleton comprised 1809 base pairs with different gene sequences. Different base substitutions were recorded at nucleotide positions 497, 499, 501 and 712 and it was possible to exploit the technique in order to clearly identify commercial root samples (Fushimi et al., 1996). Using PCR-RFLP (polymerase chain reaction—restriction fragment length polymorphism) coupled with MASA (mutant allele specific amplification), the differences of the 18S rRNA gene sequences were explored for the same three species. In this case the PCR product of each species on the 18S rRNA gene was digested with the restriction enzymes BanII and DdeI; the resultant fragments gave unique electrophoretic profiles for each species. The extracted DNA of each species was amplified by PCR using a designed species-specific oligonucleotide primer. The anticipated sizes of the fragments specific to each species were detected only when the optimum temperature and reaction time for annealing and extension were met (MASA analysis). Both methods were used on the three species drugs and produced similar results to those for the corresponding original plants. The gene sequences of the three Panax species comprised 1259 base pairs and that of P. quinquefolium varied markedly at nucleotide position 102 (Fushimi et al., 1997). Further work should offer a better understanding of species differentiation in the Araliaceae.
The work of Wen and Zimmer (1996) considered the sequences of internal transcribed spacers and the 5.8S coding region of the nuclear ribosomal DNA repeat for 12 species of Panax in the hope of establishing phylogenetic relationships. The North American species P. quinquefolium and P. trifolium were distinct, the former probably being more closely related to the eastern Asiatic species. The monophyly of the three important medicinal species P. ginseng, P. notoginseng and P. quinquefolium which had been suggested by earlier workers was not supported by current data although the close phylogenetic relationship of the genera Panax and Aralia was confirmed. The authors did, however, warn that a discrepancy between the sequence divergence pattern and the phylogenetic pattern encountered in their work did emphasise the need for caution in using sequence divergence data alone when investigating biogeographical patterns. As the Himalayan area and central and western China are the current centres of diversity of the genus Panax and the species located there appear closely related with low internal transcribed spacer sequence divergence it is suggested that rapid evolutionary radiation of the plants may have produced the diverse variations of the species.
Panax ginseng C.A.Meyer; Chinese, Korean or Oriental ginseng. This species is the most important commercially and is widely cultivated in China and Korea. Because of the wide use of the plant with resultant overharvesting, wild populations that once spread from central China, to Siberia and Korea are now scarce and are found principally in mixed broadleaf and coniferous forest areas in Manchuria. P. ginseng was found in the mixed forest areas in Heilongjiang, Jilin Kirin (Manchuria), Liaoning (adjoining North Korea) and northern Hopei (Hu, 1976) and the occurrence of rare wild populations in the Long White Mountain area of northeastern China and neighbouring Korea were reported also by Hu (1978). Typical roots are persistent, thick, fleshy, fusiform and cream to pale yellowish buff in colour; the primary root is frequently irregularly branched (Fig. 2). Older roots are wrinkled due to the annual contractile activity that maintains the position of the dormant bud at soil level. Root shape varies markedly according to the soil environment. Heavy stony soils cause short, thickened primary roots with many thickened secondary roots. Light, sandy soils produce longer, straight, carrot-like tap roots with less secondary branching. Fresh roots possess a strong taste that is bitter yet also sweet and a prominent, characteristic aroma that is gradually lost on storage. The rhizome or underground stem, which is normally unbranched, usually bears adventitious roots which may become thick and fleshy. In wild P. ginseng the rhizome may be elongated but cultivated plants yield short, thick, compact,
erect rhizomes (Baranov, 1966; Thompson, 1987). Rhizomes bear leaf scars the number of which gives an indication of the age of the plant. The leaves, also known as prongs, may be 3-6 in number in a whorl and are palmately compound, verticillate (whorled) and petiolate, the petioles being 8-15 cm long, slender and terete (smooth and rounded). Each leaf comprises 5, or occasionally 3-7, leaflets, the basal pair being smaller than the upper leaflets. Typical leaflets are serrate, cuneate (wedge-shaped) at the base, acuminate (tapering to a point)
at the apex and bear some stiff hairs along the marginal veins. The floral arrangement or inflorescence is an umbel, a flower cluster in which the flower stalks are of almost equal length and arise from a common centre. The fruit stalk or peduncle of the umbel varies from 7-20 cm long and the terminal umbel comprises 4-40 flowers dependent on the age and growth environment of the plant. The small flowers of ginseng expand in June-July and are about 23 mm across. Each consists of a 5-toothed green calyx, 5 yellowish-green entire petals, 5 short stamens with oblong anthers and a bifid style and stigma with an inferior ovary. The fruit is about the size of a common pea; initially it is green but reddens as it matures to form a fleshy drupe containing 2-3 white seeds which are often called pyrenes.
Panax japonicum C.A.Meyer=P. pseudoginseng Wall, subsp. japonicus Hara; Japanese ginseng. Chikusetsu ginseng. Also the subspecies P. japonicus var. major (Burk.) Wu and Feng and P. japonicus var. bipinnatifidus (Seem.) Wu and Feng. Zhujieshen or Rhizoma Panacis japonici, the dried rootstocks of P. japonicus, and zhuzishen or Rhizoma Panacis majoris, the dried rootstocks of P. japonicus var. major or P. japonicus var. bipinnatifidus are officially listed in Volume I of the Chinese Pharmacopoeia, 1985.
Preferring a warmer climate, this species is found in areas stretching from Japan through temperate and subtropical parts of China to the borders of northern India and Nepal. Indigenous to the mountain areas of Japan it is known locally as nin-jin or chikusetsu nin-jin. The aerial plant closely resembles P. ginseng but the rhizome is thick and horizontal with short internodes and resembles bamboo. Being more bitter than P. ginseng roots, Japanese ginseng roots are less valued commercially.
Panax notoginseng (Burk.) F.H.Chen; P. pseudoginseng Wallich; Sanchi ginseng. Several subspecies of wild Asiatic origin are recognised including subsp. himalaicum (Burk.) Wu and Feng (not currently listed in the Kew Index), subsp. japonicum (Nees) Hara (not listed in the Kew Index), subsp. pseudoginseng (not listed in the Kew Index), var. japonicus (C.A.Meyer) Hoo and Tseng, var. angustifolium (not listed in the Kew Index), var. bipinnatifidum (not listed in the Kew Index), var. elegantior (Burk.) Hoo and Tseng, var. notoginseng (Burk.) Hoo and Tseng, var. wangianus (Sun) Hoo and Tseng (Thompson, 1987). Sanchi or sanqi, Radix Notoginseng, the dried roots of P. notoginseng, is listed in Volume I of the official Chinese Pharmacopoeia, 1985.
This species is indigenous to northeast China particularly in the mountainous areas of the provinces of Heilongjiang, Jilin Kirin (Manchuria), Liaoning (adjoining North Korea) and northern Hopei (Hu, 1976). Its ecological range and therefore potential cultivation does extend westwards to include Nepal, northern India, northern Burma and southeastern Tibet. Therefore it has been reported in the Sichuan (Sze-chwan) and Kiang-su provinces of China, North Vietnam, the forested slopes of the Himalayas and northern India.
The growth habit of this species resembles that of P. ginseng. Typical roots are fleshy, firm, obconical or shortly cylindrical, smooth skinned and yellowish green to brownish yellow in colour. Roots are usually about 2-4 cm long and 1-2 cm diameter. Var. elegantior possesses a slender rhizome with elongated internodes and enlarged nodes giving the appearance of a string of pearls, hence the common name Pearl Ginseng. The root of P. notoginseng tastes bitter initially but the after-taste is sweetish.
Although indigenous to North America, this slow growing, perennial, herbaceous species rarely occurs in Western medicinal products but is used as crude drug in the Far East. P. quinquefolium is distributed in the eastern temperate forest areas of North America from southern Quebec to Minnesota in the north to Oklahoma, the Ozark Plateau and Georgia in the south. American ginseng is not found in the prairie regions and its distribution density in the eastern areas is variable due to overharvesting and habitat destruction (Carpenter and Cottam, 1982; Thompson, 1987). This species has been reported in 33 states but it is now considered as a threatened species in 16 states and as an endangered species in a further 10 states. Wild mountain ginseng from Wisconsin, Pennsylvania and New York States is considered the most desirable commercially although commercial American ginseng is usually cultivated.
P. quinquefolium resembles P. ginseng in growth habit, attaining a height of about 25-50 cm. The thick, spindle-shaped, fleshy root is persistent, up to about 10 cm length and 2.5 cm thickness and often transversely wrinkled. Older roots are usually forked or branched producing the characteristic anthropomorphic appearance so exaggerated in earlier drawings of ginseng roots. Correctly dried roots lose about 60 per cent of their initial weight and are firm and solid with a slight aromatic odour and the taste is bitter at first with a sweetish after-taste. Average dried roots weigh 30-60 g and rarely exceed 150 g. The rhizome is erect. The young seedling usually produces a whorl of 3 palmately compound leaves, the leaf is borne on a 2-10 cm petiole and possesses 3 large upper and 2 small lower leaflets as in P. ginseng. From the third year onwards the plant usually produces 3-5 compound leaves. The smaller leaflets are normally up to 5 cm long and the larger leaflets attain up to 10 cm in length. The leaves are bright green in the summer and turn yellow in the autumn. The umbel of greenish-white flowers is borne on a single stalk 5-12.5 cm long. The fruits are bright red drupes which are often miscalled "berries" and appear conspicously after about three years growth. The rapid differentiation of P. quinquefolium and P. ginseng roots by genomic fingerprinting has been successfully investigated using the arbitrarily primed polymerase chain reaction (AP-PCR) technique (Cheung et al, 1994).
Panax trifolium L.Dwarf American ginseng or groundnut ginseng. This species is hardier than P. quinquefolium. It occurs in an area embracing Nova Scotia and Ontario in Canada and spreading eastwards to Minnesota and southwards to Kentucky, Tennessee, North Carolina and northern Georgia. P. trifolium is a rapidly growing species with vegetative proliferation between April and June. It can tolerate wetter soil conditions and stronger light intensities than P. quinquefolium. It is characterised by a small, globose root attaining a diameter of 1-2 cm. The vertical rhizome is short and straight with short internodes. The smooth, hairless, annual aerial stem differs from stems of the other common species being cylindrical at the base and polygonal towards the apex. The palmately compound leaves are typical of Panax spp. (Thompson, 1987). Although not considered desirable commercially, P. trifolium may occur as an adulterant.
Panax vietnamensis Ha. et Grushv. Vietnamese ginseng. One of the lesser species, P. vietnamensis is found in forests in Central Vietnam in the wide area south of Da Nang at latitude 15° N and 108° E at elevations of 1700-2000 m above sea level. This species is characterised by a mainly unilocular ovary with one style and the fruits bear a black spot on the apex when ripe and are usually one-seeded (85 per cent), the seeds being kidney-shaped (Nguyen Thoi Nham et al., 1995).
The plant is apparently restricted to the southeastern area of Yunnan Province. The root system comprises numerous fleshy tuberous roots arising from a short rhizome.
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