1250

12(2): Medicinal and poisonous plants 2

Platycladus orientalis (L.) Franco

Portugaliae Acta Biol., Sér. B, Sist. Vol. 'Julio Henriques': 33 (1949).

CUPRESSACEAE

2n = 22

Thuja orientalis L. (1753), Platycladus stricta Spach (1841), Biota orientalis (L.) Endl. (1847).

Chinese arbor-vitae, biota (En). Thailand: chantayee (northern), son phaeng (Bangkok), son haang sing (central). Vietnam: tr[aws]c b[as], tr[aws]c b[as]ch di[eej]p.

The natural distribution of Platycladus orientalis is obscured by its long history of cultivation in large parts of Asia. It is assumed to have originated from northern and north-eastern China, Korea and the Russian Far-East. Its distribution has long extended to Japan, Taiwan and Central Asia. It is locally naturalized in Indo-China. It has been cultivated in Europe since the first half of the 18th Century.

In traditional Chinese medicine the leaves of Platycladus orientalis are credited with bitter stomachic, refrigerant, astringent, diuretic, tonic and antipyretic properties. A decoction or the juice of the leaves has been used to relieve all kinds of bleeding, duodenic and gastric ulcers, gonorrhoea and colds. The seeds are prescribed as sedative, tranquillizer, antitussive and haemostatic. In Indo-China the ground leaves are used as an emmenagogue, haemostatic and antitussive, the seeds as a tonic, sedative, tranquillizer and aphrodisiac. A decoction of the twigs is prescribed to treat dysentery, skin affections and cough. In Thailand, the leaves are used as antipyretic, diuretic, anti-inflammatory and anticough.

Dried herbal materials of Platycladus orientalis are traded from Asia. Retail prices in 2001 amounted to US$ 7 for 500 g dried leaves, US$ 8.7 for 100 g of extract granules of leafy parts and US$ 12 for 100 g of extract granules of charred leafy parts.

The leaves and fruits of Platycladus orientalis contain an essential oil which can be easily obtained by steam distillation. The leaf essential oil contains high amounts of 'ALFA'-pinene, 'BETA'-caryophyllene, cedrol, 'BETA'-myrcene, R-(+)-limonene and aloaromadendrene. The essential oil from the fruits contains high amounts of 'ALFA'-pinene, 'DELTA'-3-carene, 'BETA'-terpinene, rho-cymene, cedrol, camphene, D-limonene and myrtenol. In Egyptian material the highest yield was obtained from fresh fruits (0.32 % v/w).
Furthermore, a labdane-type diterpene, pinusolide was isolated from the hexane and chloroform extracts of the leaves of Platycladus orientalis. Pinusolide is a potent platelet activating factor (PAF) receptor-binding antagonist, which inhibited PAF-induced aggregation of rabbit platelets (IC₅₀ value of 5 µM), but had no inhibitory effect on ADP-, thrombin-, or collagen-induced platelet aggregation. Pinusolide also protected mice from PAF-induced lethality (ED₅₀ values of 1.1 mg/kg, intravenous, and 69 mg/kg, per oral). Topical administration of pinusolide, at 2 mg/ear, was effective in inhibiting croton oil-induced mouse ear oedema. Ears of treated mice fully recovered, in contrast to the necrotized ears of their untreated controls.
The effects of pinusolide on PAF-induced [3H]serotonin release from rabbit platelets, hypotension and vascular permeability were furthermore confirmed. Pinusolide (IC₅₀, about 5 x 10^-6 M) inhibited specifically [3H]serotonin release from rabbit platelets when stimulated with PAF (5 x 10^-8 M), but showed no effect when induced by ADP, collagen and thrombin. It also inhibited PAF-induced hypotension in a dose-dependent manner in rats with no effect on the hypotension induced by acetylcholine, histamine and serotonin. The inhibitory effect of pinusolide on the PAF-induced vascular permeability is less specific than the induced hypotension. The results suggest that pinusolide may prove of therapeutic value in the treatment of hypotension and a molecular design of pinusolide analogues may provide the possibility of new PAF specific antagonists.
The related compound pinusolidic acid, obtained from the CHCl₃ extract of Platycladus orientalis, also inhibited PAF-induced aggregation of rabbit platelets (IC₅₀ value of 2.3 x 10^-5 M).
In an experiment with mice, an ethanol extract of the seeds of Platycladus orientalis was investigated for its effect on learning impairment, produced by bilateral lesion of basal forebrain, and judged by performance in the step-through and step-down type passive avoidance tests. Chronic oral administration of the ethanol extract at a daily dose of 250 or 500 mg/kg, from the day of surgery until the end of the behavioural test, dose-dependently improved memory acquisition impairment in the step-down test, and memory retention disturbance in both behavioural tasks. Other effects of extracts include the haemostatic properties of the leaves, which are confirmed in a series of experiments in rabbits and dogs, aqueous and ethanolic extracts which showed marked in vitro and in vivo antitumour activity, and a decoction of the leaves which is reported as having an activity similar to that of vitamin K.
In a preliminary antibacterial screening the aqueous extract of Platycladus orientalis inhibited the growth of gram-positive bacteria at minimum inhibitory concentration of less than 3.9 mg/ml. Aqueous extracts of Platycladus orientalis significantly inhibited aflatoxin production of Aspergillus parasiticus on agricultural commodities, including rice, wheat, maize and groundnut.
Immunosuppressant activity was observed in mice fed with a diet containing 10% seed oil.

A large shrub or small to medium-sized tree, rarely exceeding 20 m tall, in cultivation often forming multiple stems; habit dense, usually broadly conical with ascending branches from bare stems; bark thin, reddish-brown, exfoliating in thin longitudinal strips; branches with the foliage held in vertically aligned sprays that always point upwards. Leaves decussate, scale-like, size correlated with growth of the shoots; leaves on leading shoots continue to elongate until after some years they wither and break up, leaves of finer lateral sprays about 2 mm long, tightly adpressed; foliage pale green, odourless when crushed. Inflorescence a unisexual cone. Male cones terminal, 2—3 mm long. Female cones oblong, 20—25 mm long, 10—18 mm wide when closed, usually with 6—8 fleshy scales, with a deeply recurved horn below the tip of each scale. Scales glaucous when growing, maturing and ripening to bright brown before opening; lower 4 scales fertile with 2(—3) seeds. Seed ovate, wingless, 5—7 mm long, 3—4 mm in diameter.

In Vietnam, Platycladus orientalis flowers in March—April, and fruits in June—August. In trials in Kazakhstan on the eastern shore of the Caspian Sea Platycladus orientalis started fruiting at 3 years.

Platycladus orientalis belongs to a monotypic genus closely related to Thuja. It can be easily distinguished by the vertical arrangement of its sprays of foliage, which lack odour when crushed, the strongly hooked bract tips of the cone scales and its wingless seeds. Numerous cultivars are registered in horticultural trade, ranging from dwarf forms to small trees; some with juvenile needle-like leaves, others green golden, slightly variegated or with filamentous branches.

In its assumed native habitat, Platycladus orientalis usually grows on steep rocky hillsides and cliffs. This explains the success of plantings on poor, excessively drained soils even with a high pH, as well as the success of smaller cultivars in rock and succulent gardens.

Platycladus orientalis can be raised easily from cuttings and seed, and the young plants adapt to most soil types and sites. Its cultivars are best raised from cuttings, but side-veneer grafting is the best option for those that prove most difficult.

Platycladus orientalis prefers full sun but is tolerant of partial shade. Growth performance of seedlings is enhanced by NPK application. NPK treatment at 10:20:10 markedly increases stem diameter. The high level of P in NPK mixtures increases root length and the number of branches. The fresh and dry weight of leaves greatly increases with increasing N and P levels in NPK treatment. Total soluble sugars generally increase as N level increases, but total soluble phenols decrease.

Leafy parts of Platycladus orientalis can be collected whenever the need arises. Mature fruits are generally collected in autumn.

Leafy parts of Platycladus orientalis can be dried and stored for future use. The seeds are obtained by opening the dried fruits and used fresh or after extraction of the essential oil.

Platycladus orientalis has a large area of distribution, either naturally or as a result of cultivation, and does not seem to be at risk of genetic erosion.

The potential for cultivation of Platycladus orientalis in South-East Asian countries especially at higher elevations needs further investigation. Pinusolide shows interesting activity in the field of hypertension and platelet activating factor (PAF-)antagonism. Although more research will be needed, the compound or its (semi-)synthetic analogues may have some potential in future medicinal research.

Chen, C.P., Lin, C.C. & Namba, T., 1987. Development of natural crude drug resources from Taiwan VI. In-vitro studies of the inhibitory effect of 12 microorganisms. Shoyakugaku Zasshi 41(3): 215—225.
Kim, K.A., Moon, T.C., Lee, S.W., Chung, K.C., Han, B.H. & Chang, H.W., 1999. Pinusolide from the leaves of Biota orientalis as potent platelet activating factor antagonist. Planta Medica 65(1): 39—42.
Morgan, C.S., 1999. Platycladus orientalis. Cupressaceae. Curtis=s Botanical Magazine 16(3): 185—192.
Nishiyama, N., Chu, P.J. & Saito, H., 1995. Beneficial effects of biota, a traditional Chinese herbal medicine, on learning impairment induced by basal forebrain-lesion in mice. Biological and Pharmaceutical Bulletin 18(11): 1513—1517.
Yang, H.O. & Han, B.H., 1998. Pinusolidic acid: a platelet-activating factor inhibitor from Biota orientalis. Planta Medica 64(1): 73—74.
Yang, H.O., Suh, D.Y. & Han, B.H., 1995. Isolation and characterization of platelet-activating factor receptor binding antagonists from Biota orientalis. Planta Medica 61(1): 37—40.

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S. Aggarwal

Aggarwal, S., 2001. Platycladus orientalis (L.) Franco. In: van Valkenburg, J.L.C.H. and Bunyapraphatsara, N. (Editors): Plant Resources of South-East Asia No 12(2): Medicinal and poisonous plants 2. PROSEA Foundation, Bogor, Indonesia. Database record: prota4u.org/prosea