Characters and Microscopic Identification of Aralia cordata

Pengfei XIA, Kaibin LI, Xiaoyan WANG, Lina LONG, Shimei ZHAO, Juan BAO

Anshun Food and Drug Inspection Institute, Anshun 561000, China

Abstract [Objectives] Characters and microscopic characteristics of Aralia cordata were studied, to improve identification method for Aralia cordata. [Methods] Using pharmacognostic identification method, original plant morphology of Aralia cordata was observed, and microscopic observation of its root cross section and powder was conducted. [Results] It is perennial herb, with rhizome recess, arranged in clusters of nodules. There are double or triple pinnate compound leaves. It is glabrous or sparsely pubescent, with umbel. Flowers are white, while fruits are spherical and purple black. In microstructure, the cork layer on the cross section of root consists of 6-10 rows of cells, and there is secondary cortex. The parenchyma cells are rich in starch granules, and the cambium is not obvious. The vessels are uniserial, and the wood fiber is less, and the primary xylem is bipartite. There are many starch granules in powder, mostly single granules, round or quasi round, oval, umbilicus herringbone or short slit, with many marginal pits and reticulate ducts. Calcium oxalate cluster crystals are mostly gathered. Cork cells are yellowish brown and arranged neatly. The fibrous wall is thin, and the pore groove is obvious, and stone cells are occasionally seen. [Conclusions] Using character and microscopic identification method, it could accurately identify medicinal material of Aralia cordata, and provide reference basis for development and utilization of its resources.

Key words Aralia cordata, Character identification, Microscopic identification

1 Introduction

Aralia cordata is dry rhizome of cultivarAraliacordataThunb., and has the functions of expelling wind and dampness, promoting blood circulation, and relieving pain. It is used to treat wind cold dampness arthralgia, waist and knee pain, Shaoyin wind pain[1]. The chemical constituents of Radix Angelicae sinensis are mainly organic acids, amino acids, tannin saponins,etc.[2-3], and organic acids have anti-inflammatory and analgesic effects[4-5]. The tender stems and buds of aboveground part in early spring are edible, which could be cold and dressed with sauce, fried or pickled. They taste delicious and rich in nutrition, and are in short supply locally. At present, Aralia cordata is mainly from wild resources, with less artificial breeding. Moreover, most of the related studies focus on the chemical composition and pharmacology, less on the description of its characters and microscopic identification. Moreover, the description of its original plants is even rarer, resulting in some obstacles to the utilization of resources. Therefore, original plant and medicinal properties of Aralia cordata were described. Moreover, microscopic study of its root sectioning and powder was conducted. It was expected to accurately identify Aralia cordata, and provide the basis for rationally developing and utilizing Aralia cordata.

2 Materials and methods

2.1 Material sourceIt was collected from the Leigong Mountains of Qiandongnan Miao and Dong Autonomous Prefecture of Guizhou. Via the identification of Professor Sun Qingwen from Teaching and Research Office of Medical Plant Cultivation and Identification, School of Pharmacy, Guizhou University of Traditional Chinese Medicine, it wasA.cordataThunb.

2.2 Reagents and instrumentsFAA stationary liquid (home-made), ethanol, formaldehyde, chloral hydrate, phloroglucinol, concentrated hydrochloric acid, diluted glycerin, distilled water,etc.DM500 type of LEICA photographic microscope (Leica Microsystems), LEICA RM2245 semi automatic slicer (Leica Microsystems), DHG-9053A electric thermostatic blast drying oven (Shanghai Xinnuo Instrument Group Co., Ltd.).

2.3 MethodsA.cordataThunb. in the wild was taken photo, and the original plant was described. The samples were excavated and dried for character identification. Fresh rhizomes were fixed with FAA stationary liquid. Using paraffin sectioning, it was made into permanent slices after dehydration, wax dipping, embedding and slicing. After drying, the rhizome was crushed and sieved through No.5 sieve, and an appropriate amount of powder was taken and loaded into slice with dilute glycerin and chloral hydrate. The above slices were observed under the electron microscope, and the digital imaging system was used for analysis and record.

3 Results and analysis

3.1 Original plant morphologyIt is perennial herb. Rhizome is overall long cylindrical, with multiple pits, and arranged in a cluster of nodules. Aerial stem of plant is 0.5-3.0 m high, which is strong, and base diameter is 1-3 cm. There are double or triple pinnate compound leaves. Petiole is 15-30 cm long, and it is glabrous or sparsely pubescent. Stipules accrete with petiole base, 3 mm long, with cilium on the margin. Pinnae has 3-5 leaflets. The leaflets are membranous, long ovate, 4-15 cm long and 3-7 cm wide. The apex is sharp, and the base is round. The base of the lateral leaflets is skewed, and the upper part is glabrous, while the lower veins are sparsely pubescent. There is coarse sawtooth on the edge, and the base has 3 radial veins, and the middle vein has 6-8 pairs of lateral veins. The petiolule is 2.5 cm long, and the terminal petiole is 5 cm long. Panicles is large, terminal or axillary, sparse. There are few branches, bearing several racemose umbels, with a umbel diameter of 1.5-2.5 cm. Peduncle is 1-5 cm long, with pubescence. Bract is linear, 3-5 mm long. Pedicel is usually filiform, 10-12 mm long, with pubescence. Bracteole is 2 mm long, and flower is white. Calyx is glabrous, 1.2-1.5 mm long, and 5 triangular sharp teeth are on the edge. There are 5 petals, which is ovate triangular, 1.5 mm long. There are 5 stamens, which is 2 mm. There are 5 ovaries, and 5 styles are distinct. The fruit is spherical and purplish black, and diameter is about 3 mm, and there are 5 ridges. Persistent style is 2 mm long and distinct, or accretes only at base (Fig.1).

Note: A. Front of original plant; B. Fruits and leaves of of original plant.

3.2 Character identification of medicinal materialsThe rhizome is cylindrical, curved and twisted, 30-80 cm long, and diameter is 3-9 cm. The surface is brownish brown to yellowish brown and rough. There are many pits on it, which are arranged in clusters of nodules. The diameter of the pits is 1.5-2.5 cm, and the depth is about 1 cm. There are residual stem marks inside. Most cylindrical roots are scattered at the bottom and side, 2-15 cm long. The diameter is 0.4-1.0 cm, and there is longitudinal stria (Fig.2). The cross section of the root has a wooden core. The rhizome is slightly light, hard, brittle, and fibrous, with yellowish white cross section and cracks (Fig.3). It is slightly fragrant, bitter and pungent.

Fig.2 Appearance characteristics of Aralia cordata medicinal materials

Fig.3 Appearance characteristics of Aralia cordata decoction pieces

Note: 1. Cork layer; 2. Starch granule; 3. Phloem; 4. Secretory cell; 5. Cambium; 6. Wood fibre; 7. Xylem; 8. Vessel; 9. Wood ray.

Note: 1. Calcium oxalate cluster crystal; 2. Vessel; 3. Cork cell; 4. Fiber; 5. Stone cell; 6. Starch grain.

3.3 Microscopic identification

3.3.1Cross section of root. Cork layer has 6-10 layers of cells, and secondary cortex has 4-5 layers of cells. Phloem accounts for 2/3 of root, and there are more secretory cells. The parenchyma cells are rich in starch granules, and the ring of cambium is not obvious. The xylem is complete, and the vessel is single row, with a diameter of 25-100 μm. Wood fiber is less and clustered. The ray width is 1-7 rows of cells, and the primary xylem is diarch (Fig.4).

3.3.2Powder. The powder is grayish yellow. There are many starch grains, mostly single grain, with a diameter of 10-40 μm. It is round or quasi round, ovoid, umbilicus herringbone or short suture. There are many bordered pits and reticulate vessels, with a diameter of 70-200 μm. Calcium oxalate cluster crystals are mostly gathered, with a diameter of 25-50 μm. Cork cells are yellowish brown and arranged neatly. The fiber wall is thin, and the pore groove is obvious, and the diameter is 20-40 μm. Stone cells are occasionally seen (Fig.5).

4 Discussion

Main identification points of morphological characteristics of original plant: the foundation is strong. With the increase of years, a pit is formed after the seedling inversion in winter every year, which is similar to the eye socket and arranged in series. The rhizome has obvious characteristics, which is an important feature to identify the original plant of Aralia cordata. There are double or triple pinnate compound leaves, which are glabrous or sparsely pubescent. It is umbel, and the fruit is spherical and purple black. Key points of microscopic identification of medicinal materials: the phloem is broad, accounting for about 2/3 of the root, and phloem has larger and more gap. The cambium is annular but not obvious, and the wood rays are mainly concentrated in the xylem. In the powder microscope, it can be seen that the starch granules are mostly single granules, umbilicus herringbone or short slit. Additionally, there are calcium oxalate crystals, cork cells, fibers, stone cells,etc.The above characteristics selected from different levels can be used as the species identification characteristics of Aralia cordata, in order to provide a scientific basis for species identification of Aralia cordata.