Studies on Commercial Cinnamon and Allied Barks. X.1, 2) on Nikkei, Cinnamomum Sieboldii MEISN., Syn

1464 Vol. 35 (1987)

Chem. Pharm. Bull. 35( 4 )1464- 1478 (1987)

Studies on Commercial Cinnamon and Allied Barks. X.1, 2) On Nikkei, Cinnamomum sieboldii MEISN., syn. C. loureirii auct. Japon non NEES

AYA NITTA

Faculty of Pharmaceutical Sciences, Kyoto University, Sakyo-ku, Kyoto 606, Japan

(Received August 25, 1986)

Japanese cinnamon on the market was investigated histologically using specimens collected in Japan. Sixteen lots of material were inspected. They were found to be diverse in internal structure with respect to the amount and combination of mechanical tissue in the bark. In addition, the difference between the Nikkei root bark and stem bark was clarified. Neither fiber bundles nor a cutinized cell layer was observed in the root bark, which had tangentially elongated cork cells, large oil cells in the primary cortex, and less mechanical tissue than the stem bark. Marketed samples exhibiting a cutinized cell layer probably contain bark from exposed roots or are adulterated with stem bark. Botanical specimens of the following Cinnamomum species were also examined histologically: Nikkei, C. sieboldii syn. C. loureirii; Yabu- nikkei, C. insularimontanum syn. C. japonicum; Kusunoki, C. camphora; Maruba-nikkei, C. daphnoides; and Shiba-nikkei, C. daphnoides subsp. Doederleinii. The root bark structures of these species were compared at five growth stages and are described in detail. At maturity, three types of structure could be distinguished. One type is shown by Nikkei and Yabu-nikkei. The second is Kusunoki, which has anatomical features not found in other species. Maruba-nikkei and Shiba-nikkei, which differ noticeably only in the amount of mechanical tissue, exhibit the third type of structure.

Keywords •\ histology; Nikkei; Japanese cinnamon; C. sieboldii; C. loureirii; C. insularimontanum; C. camphora; C. daphnoides; C. daphnoides subsp. Doederleinii; Lauraceae

Japanese cinnamon, Nikkei, was introduced from China and cultivated in various places in Japan about 260 years ago in the Edo era.3) Both its stem and root bark were used as a substitute for cassia bark obtained from Cinnamomum cassia PRESL, one of the most important drug materials in Kampo. Furthermore, root bark is preferred to stem bark for medicinal use because it has the same strong odor of cinnamaldehyde as cassia bark. Although the term " “÷Œj" (Rou qui) in Chinese denotes the thick bark from the trunk of C. cassia, the same word in Japanese is pronounced "Nikkei", and refers to both the living plant and the drug material derived from it. The scientific name of C. loureirii had been assigned to Nikkei, but recently this was revised to C. sieboldii MEISN.4) The literature concerning the identity of C. loureirii is fraught with confusions from the outset. An old source, for instance, made the highly improbable statement that it was distributed in three isolated areas, i.e. Cochinchina, the Yunnan region of China, and Japan.5) In the United States Pharmacopoeia from the 10th6) (1925) to the 14th7) (1950) revisions, it was described as the source plant of Saigon cinnamon imported from Cochinchina. Many pharmacists and plant taxonomists doubted the accuracy of this assignment. In particular, after comparing Saigon cinnamon with the bark of C. loureirii supplied by the Pharmaceutical Society of Great Britain, Redgrove stated that Saigon cinnamon was probably C. cassia. He reported that the two specimens had a similar taste but different odors. Notwithstanding the controversy, Youngken, who was one of the foremost American No. 4 1465 pharmacognosists of his time, described Saigon cinnamon with a microphotograph of the bark under the name of C. loureirii in his 1936 textbook.9) It seems that upon the suggestion of the well-known taxonomist K. C. Allen, Youngken had in fact compared histologically a specimen which he believed to be C. loureirii with both Saigon cinnamon and the bark of C. burmanni BL.10)He supposedly recognized differences between these three species, though neither descriptions of the other species nor the result of the comparison was mentioned in his textbook. Nikkei appeared in the Japanese Pharmacopoeia from the 4th 11)(1921) to the 7th12) (1961) editions. In the 4th and 5th13)editions both the stem and root bark were described under the name of Nikkei, but beginning with the 6th14)edition only the root bark was listed as Nikkei and Nihon-keihi. In the first interim revision of Part II of the 7th edition in 1962,15) it was deleted because the increasing import of cassia bark from China rendered it unnecessary as a substitute. Although Nikkei is no longer included in the Japanese Pharmacopoeia, its cultivation was continued in Wakayama and Ehime prefectures, and its stem, root bark and small root are still available on the market. Apart from medicinal usage, root bark and small roots are used for flavoring, and stem bark in incense products such as joss sticks. As for the internal structure of Nikkei, only the root bark was described and drawn in the Japanese Pharmacopoeia. Kimura and Ohta16) have examined the structure of root bark in comparison with stem bark, but their description is not detailed enough and contains some mistakes. This paper gives a more comprehensive account of the internal structure of Nikkei with a view to clarifying some of the confusions present in the literature. Nikkei found in commerce as well as root bark specimens from C. sieboldii are examined histologically, the latter in comparison with other Japanese Cinnamomum species.

Experimental

In the histological descriptions below, "U-form" sclerenchymatous cell denotes a partially lignified parenchymatous cell, while "O-form" denotes a longitudinally elongated and cylindrically lignified parenchymatous cell. Commercial Nikkei Marketed Material The name, part of the plant, date and place of collection, and name of the collector or

TABLE Ia . Marketed Materials Examined 1466 Vol. 35 (1987) No. 4 1467

A B

Fig. 1. Two Forms of Nikki on the Market

A: Collected near Kimiidera temple , Wakayama prefecture. B: Collected at the foot of Mt. Ishizuchi, Ehime prefecture .

A D

Fig. 2. Internal Structure of Japanese Cinnamon on the Market A, Nogi 0.6mm; B, Jo-chiri 1.6mm; C and E, Tsujikawa 2.6 and 3.9mm; D and G. Keishin 1.2 and 2.9mm: F. Nihon-keihi 1.8 mm 1468 Vol. 35 (1987) No. 4 1469

contributor are shown in Table Ia. Morphology •\ The form, size, thickness, odor and taste are described in Table lb.

Sixteen lots of material were examined. Eleven of these were root bark specimens, which were mostly chips. Of the four lots of root specimens, two were in the form of a bunch of slender roots (Fig. 1A). The other two were supplied in a special form: as a bundle composed of a slender root or roots coiled around pieces of thicker roots (Fig. 1 B). The remaining lot consisted of stem bark specimens, which were straight and bigger than root bark specimens. Among the lots of root bark, No. 6 Nihon-keihi and No. 9 Tsujikawa were large and similar in shape to stem bark. Histology Several specimens in each lot were examined with respect to the internal structure of transverse sections. Representative sections are depicted in Fig. 2, and detailed microphotographs of selected specimens are

A D

Fig. 4. Internal Structure of Japanese Cinnamon Bark on the Market A, B, C, Tsujikawa (3.9 mm); D, E, Tsujikawa (2.6mm). 1470 Vol. 35 (1987) No. 4 1471

shown in Fig. 3 (Nikki and Jo-chiri), Fig. 4 (Tsujikawa), and Fig. 5 (Keishin). In Fig. 3, microphotograph A shows a specimen of Nikki root 1.3 mm in diameter. Cork tissue comprised 10 layers of cell, and one or two of the innermost layers had lignified inner and side walls. Sclerenchymatous cell groups were arranged in a circular arc. Many large secretory cells were found in the primary cortex; most of them were oil cells with sizes ranging from R = 50 to 60 ƒÊ, T = 70 to 100 ƒÊ. Some bigger ones (of the order of R =100 ƒÊ and T = 130 ƒÊ) were also observed. Microphotograph 3B shows a specimen of Nikki, a root 2.4 mm in diameter. Cork tissue with lignified cells was several layers thick, and some cork cells were tangentially elongated to two to three times their usual size. Phellogen and phelloderm were distinct. Sclerenchymatous cell groups formed a nearly continuous circular band, and the cells had thickened inner and side walls. Fibers were observed in the secondary cortex. Mucilage cells were fewer in number than oil cells. Microphotographs 3C and D show a 1.6 mm thick sample of Jo-chiri root bark. Cork tissue was about 15 layers thick. Root bark with secondary thickening consisted of U-form sclerenchyma (sc1 ). Stone cell groups were interspersed in both cortices, and the stone cells toward the inner region were smaller and had thinner walls than those in the outer region. Microphotographs 3E and F are cross sectional views of a 0.9 mm thick sample of Jo-chiri. Cork tissue was lignified every two or three layers at the inner and side walls. Stone cells formed a broad band. There were many fibers, but U- and O-form (sc2) sclerenchyma were rare. The range of sizes of smaller stone cells in the secondary cortex was R =30 to 40 ƒÊ, T =40 to 50 ƒÊ; and that of bigger ones was R = 40 to 50 ƒÊ, T = 60 to 70 ƒÊ. In Fig. 4, microphotographs A, B and C show a 3.9 mm thick specimen of Tsujikawa. Cork tissue was 10 layers thick, and some of the cork cells were lignified. Phellogen and phelloderm were distinct. Large groups of tangentially elongated stone cells were few in number, and the sizes of individual stone cells ranged from R = 10 to 20 ƒÊ and T = 50 to 120 ƒÊ. In addition to U- and O-form sclerenchyma, few fibers were observed. Secretory cells were found in the

parenchyma at the innermost region, and prismatic and oblique-prismatic crystals were present in the medullary rays. Transectional views of a 2.6 mm thick specimen of Tsujikawa are shown in microphotographs 4D and E. The outermost region had been peeled off. Stone cells small in size and similar to O-form sclerenchymatous cells, occurred in small groups. U- and O-form sclerenchyma occupied about 4/5 of the area of the bark cross section examined. Many fibers and a few small secretory cells were observed. The sizes of fibers were R = 20 ƒÊ, T = 25 ƒÊ, and L = (150-) 300 to 350 (-400)ƒÊ. Some samples of Tsujikawa had a cutinized cell layer.

TABLE II . Specimens of Nikkei, Cinnamomum sieboldii MEISN. 1472 Vol. 35 (1987)

Microphotographs of Keishin stem bark are shown in Fig. 5. Microphotographs A, B, C and D show a sample 5.0 mm thick. A few groups of small stone cells were present. U- and O-form sclerenchyma and fibers were all small in size. Microphotographs E and F show a 2.3 mm thick specimen. O-form sclerenchyma and fibers were more numerous here than in the 5.0 mm specimen. Botanical Specimens of Japanese Cinnamomum Species 1. C. sieboldii M EISN. syn. C. loureiril auct. Japon, non N EES (Nikkei in Japanese). The specimens examined are listed in Table II. 2. C. insularimontanum HAY. syn. C. japonicum SIEB.ex NAKAI(Yabu-nikkei). 1) BHD 32 cm, 2) BHD 30 cm, 3) BHD 25 cm, 4) BHD 20 cm, November 1984, the botanic garden, Faculty of Science, Kyoto University. 3. C. camphora (L.) SIEB. (Kusunoki). 1) BHD 70 cm, 2) BHD 40 cm, 3) BHD 30 cm, November 1984, the botanic garden, Faculty of Science, Kyoto University. 4) BHD 5 cm, 5) BHD 2.5 cm, 6) BHD 1.8 cm, May 1985, the campus, Faculty of Pharmaceutical Sciences, Kyoto University. 4. C. daphnoides SIEB.et Zucc. (Maruba-nikkei). 1) BHD maximum 1.8 cm, height 170 cm, 2) height 70 cm, November 1984, the herbal garden, Faculty of Pharmaceutical Sciences, Kyoto University. 5. C. daphnoides subsp. Doederleinii KITAM. (Shiba-nikkei). 1) BHD maximum 2.0 cm, height 180 cm, November 1984, the herbal garden, Faculty of Pharmaceutical Sciences, Kyoto University. In the case of C. daphnoides and its subspecies, a single plant grows to form a cluster of trunks joined by lateral roots. Such a cluster yields correspondingly more specimens from the root-stem transition region. The odor of the root specimens was camphor-like except for C. sieboldii and C. insularimontanum. Histology Several roots in each sample, including exposed roots, were examined from the tip to the trunk border. Figure 6 depicts the internal bark structures at five growth stages corresponding to five cross sections taken from each specimen. As seen in diagrams I and II, very small root of all five species have the same structure. In I, the first stage, three

Fig. 6 . Stages of Development in the Root Bark Structure of Japanese Cinnamomum Species

I and II, all species; III-A and IV-C, C. sieboldii, C. insularimontanum and C. camphora; V-D, C. sieboldii and C. insularimontanum; V-E, C. camphora; III-B, C. daphnoides and its subspecies; IV-F and V-H, C. daphnoides; IV-G and V-J, C. daphnoides subsp. Doederleinii. No. 4 1473 1474 Vol. 35 (1987)

to four groups of single or paired U-form sclerenchymatous cells with thickened inner wall were observed. In addition, many big secretory cells, most of them oil cells, were found in the outer region of the cortex. In II, the second stage, the cork layer thickened, and fibers appeared in the secondary cortex. Sclerenchymatous cells proliferated to form an incipient ring. Further growth and differentiation continued along two developmental pathways, as shown in III-A and III-B. In III-A, fiber cells increased, and the cell wall of the ring-formed sclerenchyma had thickened to the extent that a ring of stone cells was formed. In contrast to this, the cell wall of the sclerenchyma thickened only a little in III-B. In the fourth stage, medullary rays had appeared and were clearly visible in all specimens. In IV-C, O-form sclerenchyma was interspersed in the secondary cortex, and fiber cells were more numerous. In IV-F, the sclerenchyma ring observed in III-B had become wavy in appearance. In IV-G, on the other hand, it had changed to a ring of stone cells, and O-form sclerenchymatous cells and fibers appeared inside the ring. Diagrams V-D, E, H and J show the characteristic structure of each species at maturity. In V-D, which shows C. sieboldii and C. insularimontanum, the stone cell ring was fragmented, stone cell groups and O-form sclerenchyma of various sizes were found in the secondary cortex, and the outer region of stone cell groups was filled with U- form sclerenchyma. In V-E, which depicts C. camphora, the cork layer had developed so much that the stone cell ring was sloughed off. Stone cells, generally radially elongated, form tangentially elongated groups which were arranged in a concentric array of fragmented rings. This phenomenon was not observed in the other species examined. A few O-form sclerenchyma were found outside the stone cell groups. Phelloderm was obscure. C. daphnoides is shown in V-H. Here the sclerenchyma ring was fragmented and the primary cortex was filled with U-form sclerenchyma. V-J shows C. daphnoides subsp. Doederleinii. The stone cell ring was also fragmented, and stone cell groups were found in the secondary cortex. Figures 7 to 10 depict in detail the structures of the root bark of Nikkei (C. sieboldii), Yabu- nikkei (C. insularimontanum), Kusunoki (C. camphora), Maruba-nikkei (C. daphnoides), and Shiba-nikkei (C. daphnoides subsp. Doederleinii). In Fig. 7, photographs A to E show the detailed bark structure of Nikkei, and F and G show that of Yabu- nikkei. For both species, some cork cells were tangentially elongated to three times the usual size, and phellogen and phelloderm were distinct. The stone cell ring was two to three layers thick. A few stone cell groups consisting of two to several stone cells were found in the secondary cortex. U-form sclerenchyma occurred in both the primary and secondary cortices, O-form sclerenchyma and fibers in the secondary cortex in 7A to C, and big secretory cells in

A C

Fig. 8 . Root Bark Structure of Kusunoki, C. camphora No. 4 1475

the primary cortex in 7A. Prismatic and oblique-prismatic crystals were observed throughout. In 7C, which shows a small Nikkei root that had been exposed, a cutinized layer of cells can been seen. Photograph F depicts a root of Yabu-nikkei 1.7 mm in diameter. A ring of sclerenchymatous cells had already formed, and fibers were observed. Photograph G shows a 3.2 mm root of Yabu-nikkei. Here the stone cell ring was broad and many fibers were present. Yabu- nikkei tended to have more mechanical tissue than Nikkei in the case of small roots. The sizes of fibers were R 20 ƒÊ, T = 20 to 30 ƒÊ, and L =(200-) 300 to 350 (-450)ƒÊ. Root bark specimens shown in Fig. 8 were obtained from a young tree of Kusunoki. Photographs A and B show a root 1.7 mm in diameter. A thick cork tissue, a narrow sclerenchyma ring, and many fibers were observed. Photographs A and D depict areas near the root- stem transition region. Here the stone cell ring was broad, and as shown in D, stone cell groups in the secondary cortex were in the process of shifting from a radial to a tangential arrangement. Stone cells were radially elongated and ranged in size from R =150 to 300 (-330) ƒÊ, T = 30 to 70 ƒÊ. A few O-form sclerenchyma, oil cells and rhomboid crystals were also found. The sizes of fibers were R = 20 ƒÊ, T=25 to 30 ƒÊ, and L = (250-) 350 to 450 (-550)ƒÊ. The root bark structure of Maruba-nikkei is shown in Fig. 9. Photographs A and B are cross sections of roots 2.4 mm and 4.0 mm in diameter, respectively. The sclerenchyma ring was wavy in B. Photograph C shows a 1.3 mm thick bark specimen obtained at the trunk border. Cork tissue was lignified in one to two cell layers. Phellogen and

phelloderm were distinct, and U-form sclerenchyma was found both in the primary cortex and near the stone cell groups. A few fibers were also observed. Photograph 9D shows a 1.2 mm thick bark specimen taken from the trunk border of an exposed root. In contrast to C, the outermost cell layer was cutinized, phelloderm was obscure, and primary cortex was filled with U- and O- form sclerenchyma. Fibers wtre few in number, as in C, with dimensions R =20 ƒÊ,T=25 ƒÊ, and L = (100-) 250 to 300 ƒÊ. Prismatic crystals were observed in all Maruba-nikkei specimens. Figure 10 show in detail the structure of Shiba-nikkei. Photographs A and B are cross sections obtained from the same root, where the diameters measured 1.5 and 3.0 mm, respectively. Sclerenchymatous cells found in A

proliferated to form the ring in B, and fibers, absent in A, appeared in B. Root bark specimens obtained near the trunk border were also examined. They are depicted in C and D. In C,

A C D

Fig. 9. Root Bark Structure of Maruba-nikkei, C. daphnoides D: root bark from an exposed root. 1476 Vol. 35 (1987)

C A D

Fig. 10. Root Bark Structure of Shiba-nikkei, C. daphnoides subsp. Doederleinii D: root bark from an exposed root.

the cross section of a 0.9 mm thick specimen, phellogen and phelloderm were distinct. A ring consisting of stone cells and other sclerenchymatous cells was present. Many fibers and a few O-form sclerenchyma were found in the secondary cortex. The size of fibers was L = 200 to 350 ƒÊ. The same kind of contrast found in Maruba-nikkei between bark structures of normal and exposed roots is also seen in D. The 0.8 mm thick specimen shown here was taken from an exposed root. Its outermost cell layer was cutinized, phelloderm was obscure, and the primary cortex was filled with U-form sclerenchyma. Prismatic crystals were also found in all Shiba-nikkei specimens.

Conclusion and Discussion 1) The internal structure of commercial Nikkei, root bark of C. sieboldii syn. C. loureirii, was examined in detail. It was found to vary considerably with respect to the amount and combination of mechanical tissues such as U- and O-form sclerenchyma, fibers, and stone cells of various sizes and shapes. Such structural differences arising from variations in mechanical tissues have been observed in the stem bark of C. burmanni. BC.17) The mechanical tissues of some samples were identical in structure to those observed in the stem bark of C. pseudoloureirii HAY., which was described in the previous report." 2) The differences between the root and the stem bark of Nikkei may be characterized by the following general remarks. As reported by Kimura and Ohta,16) root bark has neither cuticle nor fiber bundle. It contains big oil cells which are not present in stem bark. Such oil cells occur in the primary cortex and are more numerous in small roots. Several additional differences were noted in this investigation. Root bark involved less mechanical tissue and a more distinct phelloderm than stem bark. Also, while the cork cells in stem bark are generally uniform in size and shape, some of them in the root bark are tangentially elongated to two to three times the normal size. Furthermore, with the notable No. 4 1477 exception of bark obtained from exposed root, root bark typically lacks a cutinized cell layer. Samples that exhibit such a layer may be assumed to contain bark from exposed roots or to be adulterated with stem bark. 3) Differences between the root bark structures of Japanese Cinnamomum species were investigated by tracing the developmental changes which occurred over five stages of growth. Very small roots were found to be identical for all species examined . Three distinct types of structure can be observed in mature specimens. One type is exhibited by Nikkei and Yabu-nikkei. In these two species, the sclerenchyma ring soon changed to a stone cell ring, which then became discontinuous . Various sizes and shapes of stone cell groups consisting of isodiametrically or tangentially elongated stone cells were present in the secondary cortex. U- and O-form sclerenchyma, fibers, and prismatic or oblique-prismatic crystals were also observed. Although the two were not distinguishable, Yabu-nikkei tended to have more mechanical tissue than Nikkei in bark specimens of equal thickness. A second type is exhibited by Kusunoki, which was quite different from the other Japanese Cinnamomum species examined. Its cork tissue was thick, and tangentially elongated stone cell groups consisting of radially elongated stone cells formed a concentric array of fragmented rings. U- and O-form sclerenchyma were rare, and crystals were rhombic . Maruba- nikkei and Shiba-nikkei were nearly indistinguishable and can be considered to have a third type of structure. In Maruba-nikkei, a fluted sclerenchyma ring existed for a long time before changing to a stone cell ring. U-form sclerenchyma tended to develop from the region just under the cork layer, and crystals were prismatic. In Shiba-nikkei, the sclerenchyma ring changed to a stone cell ring before the onset of fragmentation. The form of crystals was also prismatic, but Shiba -nikkei contained more U- and O-form sclerenchyma than Maruba-nikkei. 4) Questions pertaining to the identification of C. loureirii with Saigon cinnamon in the United States Pharmacopoeia have been answered in part by this and earlier reports.1.18)

References and Notes

1) Part IX: A. Nitta, Yakugaku Zasshi, 105, 256 (1985). 2) The following abbreviations are used: k, cork cell; pd, phelloderm; cuc, cutinized cell; sc1, U-form sclerenchymatous cell; sc2, O-form sclerenchymatous cell; st, stone cell; f, fiber; mr, medullary ray; oc, oil cell; sec, secretory cell; cr, crystal; R, radial; T, tangential; L, longitudinal; BHD, breast height diameter. 3) S. Kitamura and G. Murata, "Coloured Illustrations of Woody Plants of Japan," Vol. I, Hoikusha Publishing Co., Ltd., Osaka, 1979, pp. 199-204. 4) J. Ohwi, "Flora of Japan," Shibundo, Tokyo, 1956, pp. 652-653. 5) A. D. Candolle, "Prodromus Systematis Naturalis," Regni vegetabilis, Pars XV, Sectio Prior, Victoris Masson et Filii, Parisiis, 1864, pp. 12-13, 16 (Auctore C. F. Meissner). 6) The United States Pharmacopoeial Convention Inc., "Pharmacopoeia of the United States of America, 10th Revision," Lippincott, Philadelphia, 1925, p. 111. 7) The United States Pharmacopoeial Convention Inc., "Pharmacopoeia of the United States of America, 14th Revision," Easton, Mack Printing Company, Philadelphia, 1950, pp. 142-143. 8) H. S. Redgrove, "Spices & Condiments," Sir Isaac Pitman & Sons, London, 1933, pp. 115-116. 9) H. W. Youngken, "A Textbook of Pharmacognosy," P. Blakiston's Son & Co., Inc., Philadelphia, 1936, pp. 323-325. 10) K. C. Allen, J. Arn. Arb., 20, 52 (1939). 11) H. Kondo, Y. Asahina and Y. Yasumoto (ed.), "Commentary of the Japanese Pharmacopoeia, Ed. IV," Sokyudo, Tokyo, 1921, pp. 362-363. 12) Society of Japanese Pharmacopoeia, "Commentary of the Japanese Pharmacopoeia, Ed. VII," Vol. 2, Hirokawa Book Store, Tokyo, 1961, p. 283. 13) Y. Asahina, Y. Yasumoto, N. Fujita and S. Takagi (ed.), "Commentary of the Japanese Pharmacopoeia, Ed. V," Nankodo, Tokyo, 1934, pp. 409-410. 14) Y. Asahina and S. Takagi (ed.), "Commentary of the Japanese Pharmacopoeia, Ed. VI," Nankodo, Tokyo, 1478 Vol. 35 (1987)

1951, pp. 592-594. 15) Society of Japanese Pharmacopoeia, "Commentary of the Japanese Pharmacopoeia, Ed. VII," Part II, 1962, the preface. 16) K. Kimura and N. Ohta, Yakugaku Zasshi, 69, 75 (1949). 17) S. Yoshida and A. Nitta, Yakugaku Zasshi, 96, 1385 (1976). 18) A. Nitta, Yakugaku Zasshi, 104, 261 (1984).