Jie Zhao* and Jin-shuo Ma
School of Pharmacy, Xinxiang Medical University, Xinxiang, 453003, China
Received: 21/07/2015 Accepted: 25/12/2015 Published: 03/01/2016
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The genus Cinnamomum has been reviewed for its chemical constituents and biological activities including traditional importance of some common species. The plants of this genus contain butanolides, cinnamaldehyde and its analogues, diterpenoids, lignans and others. The aim of the present paper is to review the comprehensive knowledge of the plants of this genus including the traditional uses, chemistry, and pharmacology.
Cinnamomum; Phytochemicals; Bioactivities.
The genus Cinnamomum (Lauraceae) comprises of about 250 species, which occur in Eastern Asia, Australia, and archipelago of Pacific Ocean . It is acknowledged worldwide as an important genus because of its beneficial uses of the essential oils produced by the barks, in particular, cinnamon (C. verum syn. C. zeylanicum), cassia (Chinese cassia, C. cassia syn. C. aromaticum; Indonesian cassia, C. burmannii; and Indian cassia, largely C. tamala), and camphor (C. camphora), and will be of interest to research scientists [2-4]. Cinnamomum cassia is the most famous one, scheduled as cortex cinnamomi in the Chinese pharmacopoeia , which is used for treating dyspepsia, gastritis, blood circulation disturbances, and inflammatory diseases. Its extracts contain several active components such as essential oils (cinnamaldehyde, cinnamic alcohol, cinnamic acid, and coumarin), tannin, mucus, and carbohydrates . The main constituents of C. cassia bark oil are cinnamaldehyde. It is used mainly in medicine, foods and cosmetics , and is employed in aromatherapy as a rub to promote blood circulation. It also contains both anti-fungal and anti-bacterial principles that can be used to prevent food spoilage due to bacterial contamination .
A number of plants in the genus Cinnamomum are sources of secondary metabolites with interesting chemical structures and significant bioactivities.
In this article, due to the wide variety of chemical constituents, we aim at providing an overview of the phytochemical progress and listing the compounds isolated from Cinnamomum over the period from 1980 to 2014 in worldwide distribution. The biological activities of the crude extracts and isolated compounds of this genus are also included. This review is intended to compile the constituents, verify their bioactivities, indicate potential leads for future drug design, and thus, provide a reference for further research and the application of Cinnamomum.
A total of 127 chemical constituents have been obtained from the genus Cinnamomum
Over the past three decades, including butanolides (1-19), cinnamaldehyde and its analogues (20-55), diterpenoids (56-75), dibenzocycloheptanoids (76-87), Lignans (88-100), flavonoids (101-116), as well as others (117-127), their structures are shown below, and their names and the corresponding plant sources are compiled in Table 1. These new compounds are discussed in view of the structural feature as follows.
|No.||Compound class and name||Source||Ref.|
|1||Kotomolide A||C. kotoense|||
|2||Isokotomolide A||C. kotoense|||
|3||Obtusilactone A||C. kotoense|||
|4||Isoobtusilactone A||C. kotoense|||
|5||Subamolide D||C. subavenium|||
|6||Subamolide E||C. subavenium|||
|7||Linderanolide B||C. subavenium|||
|8||Isolinderanolide B||C. subavenium|||
|9||Tenuifolide A||C. tenuifolium.|||
|10||Isotenuifolide A||C. tenuifolium.|||
|11||Kotomolide B||C. kotoense|||
|12||Subamolide C||C. subavenium|||
|13||Tenuifolide B||C. tenuifolium|||
|14||Subamolide A||C. subavenium|||
|15||Subamolide B||C. subavenium|||
|16||Secokotomolide A||C. kotoense|||
|18||Secosubamolide A||C. subavenium|||
|19||Secotenuifolide A||C .tenuifolium.|||
|Cinnamaldehyde and its analogues|
|25||Cinnamic acid||C. cassia|||
|26||Cinnamic alcohol||C. cassia|||
|27||o-coumaric acid||C. cassia|||
|29||Cinnacasolide A||C. cassia|||
|31||Methyl dihydromelilotoside||C. cassia|||
|33||4-hydroxy-3-methoxyphenethyl butyrate||C. reticulatum|||
|34||4-hydroxy-3-methoxyphenethyl hexyrate||C. reticulatum|||
|35||4-hydroxy-3-methoxyphenethyl pentadecyrate||C. reticulatum|||
|36||4-hydroxy-3-methoxyphenethyl stearate||C. reticulatum|||
|37||4-hydroxy-3-methoxyphenethyl heneicosyrate||C. reticulatum|||
|38||p-hydroxybenzoic acid||C. burmanii|||
|39||Syringic acid||C. burmanii|||
|40||Vanillic acid||C. burmanii|||
|41||Protocatechuic acid||C. burmanii|||
|42||Kobusinol B||C. zeylanicum|||
|43||Caffeic acid||C. zeylanicum|||
|44||Cinnamic acid||C. zeylanicum|||
|45||Ferulic acid||C. zeylanicum|||
|47||Icariside DC||C. cassia|||
|50||Cinnacasolide C||C. cassia|||
|51||Cinnacasside A||C. cassia|||
|52||Cinnacasside B||C. cassia|||
|53||Cinnacasside C||C. cassia|||
|54||Cinnacasside D||C. cassia|||
|55||Cinnacasside E||C. cassia|||
|60||Cinncassiol A||C. cassia|||
|61||Cinncassiol A-19-O-β-D-glucopyranoside||C. cassia|||
|62||Cinncassiol B||C. cassia|||
|63||Cinncassiol B-19-O-β-D-glucopyranoside||C. cassia|||
|64||Cinncassiol C1||C. cassia|||
|65||Cinncassiol C1-19-O-β-D-glucopyranoside||C. cassia|||
|66||Cinncassiol C2||C. cassia|||
|67||Cinncassiol C3||C. cassia|||
|68||Cinncassiol D1||C. cassia|||
|69||Cinncassiol D1-19-O-β-D-glucopyranoside||C. cassia|||
|70||Cinncassiol D2||C. cassia|||
|71||Cinncassiol D2 -19-O-β-D-glucopyranoside||C. cassia|||
|72||Cinncassiol D3||C. cassia|||
|73||Cinncassiol D4||C. Cassia|||
|74||Cinncassiol D4-19-O-β-D-glucopyranoside||C. Cassia|||
|75||Cinncassiol E||C. Cassia|||
|81||(aR)- and (aS)-Subavenoside A||C. subavenium|||
|82||(aR)- and (aS)-Subavenoside B||C. subavenium|||
|83||(aR)- and (aS)-Subavenoside C||C. subavenium|||
|84||(aR)- and (aS)-Subavenoside D||C. subavenium|||
|85||(aR)- and (aS)-Subavenoside E||C. subavenium|||
|86||(aR)- and (aS)-Subavenoside F||C. subavenium|||
|88||Lyomresmol 3α-O-β-D-glucopyranoside||C. Cassia|||
|93||Clemaphenol A||C. subavenium|||
|96||Secoisolariciresinol diferuloyl esters||C. osmophloeum|||
|97||9,9′-di-O-feruloyl-(+)-5,5′-dimethoxy secoisolariciresinol||C. osmophloeum|||
|99||(7′S,8′R,8R)-lyoniresinol-9-O-(E)-feruloyl ester||C. osmophloeum|||
|100||(7′S,8′R,8R)-lyoniresinol-9,9′-di-O-(E)-feruloyl ester||C. osmophloeum|||
|103||Kaempferol-7-O-α-L- rhamnopyranoside||C. osmophloeum|||
|107||Kaempferol 3-O-β-D-glucopyranosyl-(1→4)- α-L-rhamnopyranosyl-7-O-α-L-rhamnopyranoside||C. osmophloeum|||
|108||Kaempferol 3-O-β-D-apiofuranosyl-(1→2)- α-L-arabinofuranosyl-7-O-α-L-rhamnopyranoside||C. osmophloeum|||
|109||Kaempferol 3-O-β-D-apiofuranosy-(1→4)-||C. osmophloeum|||
|120||ethyl 3,5-dihydroxy-4-nitrobenzoate||C. tenuifolium|||
|124||Cinnamophilin D||C. philippinense|||
|127||Cinnamtannin B-1||C. zeylanicum|||
Table 1: Chemical Constituents of plants from the genus Cinnamomum.
In the course of screening for the chemotaxonomy and biologically active metabolites from Formosan Lauraceous plants, Chen and co-workers analyzed several Cinnamomum plants. Three new butanolides, kotomolide A (1), isokotomolide A (2), and kotomolide B (11), were from the leaves of C. kotoense .
Subamolides A-C (14-15, 12), and new secobutanolides, secosubamolide (17), were isolated from the stems of C. subavenium . Subamolide D (5) and subamolide E (6), and a new secobutanolide, secosubamolide A (18), were isolated from the leaves of C. subavenium . Tenuifolide A (9), isotenuifolide A (10), and tenuifolide B (13), a new secobutanolide, secotenuifolide A (19) were isolated from the stems of C. tenuifolium . Compounds 1-10 have the same hydroxy-γ-methylene-α, β-unsaturated-γ-lactone skeleton. Compounds 16-19 belong to the class of secobutanolides.
Cinnamaldehyde and its Analogues
A methanol extract of the twigs of C. cassia was found to possess inhibitory activity against tyrosinase. Purification of the MeOH extract afforded four new phenolics, cassiferaldehyde (24), icariside DC (47), cinnacassinol (48), and dihydrocinnacasside (32), together with 10 known compounds (20-23, 25-28, 30-31) . Later, cinnacasolide A–C (29, 49-50) were isolated from the same plant . Two n-hexane and CHCl3 extractions of the stems of C. reticulatum afforded a mixture of 4-hydroxy-3-methoxyphenethyl derivatives (33–37). Compounds 35-37 were new compounds . P-hydroxybenzoic acid (38), syringic acid (39), vanillic acid (40), protocatechuic acid (41) and kobusinol B (42) were isolated from stems of C. burmanii . Caffeic acid (43), cinnamic acid (44), ferulic acid (45) and eugenol (46) were purified from n-hexane and ethyl acetate fraction of the stem bark of C. zeylanicum . Cinnacassides A–E (51–55), five novel glycosides with a unique geranylphenylacetate carbon skeleton, was isolated from the stem bark of Cinnamomum cassia. Each of the cinnacassides A–D possesses one of the four stereoisomers in the aglycone. Their structures were established by extensive spectroscopic analysis and chemical and chiroptical methods .
The structures of twenty diterpenoids (56-75), isolated from the fraction exhibiting anti-complement activity of the water extractive of Cinnamomi Cortex, have been characterized by means of chemical, spectral and X-ray crystallographic analyses [19-25]. These diterpenes so far obtained from Cinnamomi Cortex can be classified into four groups. Cinnzeylanine (56) , cinnzeylanol (57) , cinncassiol B (62)  and cinncassiol B-19-O-β-D-glucopyranoside (63)  belong to the ketal type. Anhydrocinnzeylanine (58) , anhydrocinnzeylanol (59) , cinncassiol A (60)  and cinncassiol A-19-O-β-D-glucopyranoside (61)  belong to the lactone type. Cinncassiol C1 (64) , cinncassiol C1-19-O-β-D-glucopyranoside (65) , cinncassiol C2 (66)  and cinncassiol C3 (67)  belong to the diketone type. Compounds 68-74 [23,24] were the novel pentacyclic diterpene consisting of three fivenumbered rings and two six-numbered ones, and its skeleton corresponds to a migrated form from the C5-C6 into C5-C1 bond in the ketal-type diterpene. D-glucosyl moiety of compounds 61, 63, 65, 69, 71 and 74 are linked to the C-19 hydroxy group of diterpenes and is β-configuraticn.
Chen’s group found reticuol (77) in C. macrostemon and C. reticulatum , separated tenuifolin (76) from C. tenuifolium , isolated subamol (78) from C. subavenium  and also separated burmanol (79) from C. burmanii . Those dibenzocycloheptanoids which might exist in Cinnamomum plant specially. Five dibenzocycloheptatrienes (80−82, 84, and 85) and one dibenzocycloheptadiene (87) were isolated from the leaves of C. subavenium. The glycosides 81−86, named (aR)- and (aS)-Subavenoside A-F, comprise two diastereomers because of the chiral glycosyl moiety and the axial chirality of the biphenyl system .
Lyomresmol 3α-O-β-D-glucopyranoside (88) and (+)-syringaresinol (89) had been obtained from the dried bark of C. cassia . Four lignans, (+)-sesamin (91), (+)-syringaresinol(89), pluviatilol(92), and clemaphenol A(93), were isolated from the leaves of C. kotoense . (+)-Syringaresinol (89), (+)-yangambin (90) and (+)-sesamin (91) were isolated from the stems of C. burmanii . A new cyclobutane lignan, named cinbalansan (94), was isolated from the leaves of C. balansae , The structure of cinbalansan was shown to be 1β, 2β, 3α, 4α-1,2-dimethyl-(3,4-dimethoxyphenyl) cyclobutane by a combination of 1H-, 13C-NMR, and NOEexperiments and by direct analysis of the 1H-NMR spectrum by the method of X-ray. Three novel lignan esters, one dibenzylbutanetype ligan ester [9, 9′-di-O-feruloyl-(+)-5, 5′-dimethoxy secoisolariciresinol (97)] and two cyclolignan esters [(7′S, 8′R, 8âlyoniresinol- 9-O-(E)-feruloyl ester (99) and (7′S, 8′R, 8R)-lyoniresinol-9,9′-di-O-(E)âferuloyl ester (100)], and three known lignans(compounds 95-96, 98) from the heartwood and roots of C. osmophloeum .
Six flavonoids, including kaempferol (101), kaempferol 3-O-α-L-rhamno-pyranoside (102), kaempferol 7-O-α-Lrhamnopyranoside (103), kaempferol 3-O-α-L-rhamnopyrano-side-7-O-α-L-rhamnopyranoside (104), kaempferol 3-O-α-Lrhamnopyranosyl-( 1→2)- α-L-rhamno-pyranoside (105), were isolated from C. osmophloeum .
Kaempferitrin (106), kaempferol 3-O-β-D-glucopyranosyl-(1→4)- α-L-rhamnopyranosyl-7-O-α-L-rhamnopyranoside(107), kaempferol 3-O-β-D- apiofuranosyl-(1→2)- α-L-arabinofuranosyl-7-O-α-L-rhamnopyranoside (108), and kaempferol 3-O-β-Dapiofuranosy-( 1→4)- α-L-rhamnopyranosyl-7-O-α-L-rhamno-pyranoside (109) were isolated from the leaves of C. osmophloeum, a Taiwan endemic tree .
Quercetin-3-O-α-L-rhamnopyranoside (110) and rutin (111) were isolated from the water extract of cinnamon fruits of C. zeylanicum .
A chemical examination of the bark of C. cassia has led to the isolation of three flavan-3-ol glucoside (114-116) and (-)-epicatechin (113) .
Three amides, N-transferuloylmethoxytyramine (117), N-cis-feruloylmethoxytyr amine (118) and cinnaretamine (119), were isolated and identified from C. reticulatum . One new nitrobenzoate, ethyl 3,5-dihydroxy-4-nitrobenzoate (120) was isolated from leaf extract of C. tenuifolium . This is the first report of Cinnamomum metabolites with a nitro benzenoid derivative. Two novel Cinnamomum normonoterpenoids, subamone (121) has been isolated from C. subavenium , reticuone (122) has been isolated from C. reticulatum Hay . A new C19 γ-lactone, cinnakotolactone (123), was isolated from the n-hexane layer of the leaf extracts of C. kotoense . Cinnamophilin D (124) was isolated from the leaves of C. philippinense . One novel benzodioxocinone, 2, 3-dihydro-6,6-dimethylbenzo-[b][1,5] dioxocin-4(6H)-one (125) was isolated from the leaves’ extract of C. tenuifolium .
Two phenolic derivatives, urolignoside (126) and cinnamtannin B-1 (127), were isolated from the water extract of cinnamon fruits of C. zeylanicum  (Figure 1).
The traditional medicinal applications of the Cinnamomum species have inspired many pharmacological investigations. The secondary metabolites from genus Cinnamomum possess various biological properties, which were mainly cytotoxicity, antiinflammatory, antioxidant, NF-κB inhibitory and tyrosinase inhibition activity.
Secokotomolide A (16), isolated from the leaves of C. kotoense, was found to induce significant cell death in the human HeLa cell line. Apoptotic-related DNA damage can be positively related to the dose of secokotomolide A .
Propidium iodide staining and flow cytometry were used to evaluate DNA damage of the treated SW480 cells, and it was found that five new butanolides and one secobutanolide, subamolides A-E (14-15, 12, 5-6) and secosubamolide (17) caused DNA damage in a dose-dependent manner after 24 h of treatment. At a 100 μM concentration, all compounds induced significant damage to DNA. The order of potency in inducing DNA damage was observed to subamolide E (6) > subamolide D (5) > subamolide B (15) > subamolide A (14) > secosubamolide (17) > subamolide C (12) [10-12].
Isoobtusilactone A (4), a constituent isolated from the leaves of C. kotoense, was investigated the anticancer effect on human non-small cell lung cancer (NSCLC) A549 cells. Isoobtusilactone A was found to induce the arrest of G2-M phase, induce apoptosis, increase sub-G1, and inhibit the growth of these cells. Further investigation revealed that isoobtusilactone A’s blockade of the cell cycle was associated with increased levels of p21/WAF1, p27kip1, and p53 .
A new secobutanolide, secotenuifolide A (19) was discovered to induce apoptotic-related DNA damage, increase sub-G1 cells, and inhibit the growth of human prostate cancer cells, DU145 .
(7′S, 8′R, 8R)-lyoniresinol-9,9′-di-O-(E)-feruloyl ester (100) from C. osmophloeum has strong activities against human liver cancer (HepG2 and Hep3B) and oral cancer (Ca9-22) cells, with IC50 values of 7.87, 4.31, and 2.51 μg/mL .
Subamone (121) was demonstrated to have cytotoxicity against A549, DU145 and LNCaP cell line (pIC50 was: 2.24±0.03, 2.42±0.01 and 7.01±0.04, respectively). Subamone was also found to be significantly active against LNCaP cell line (prostate cancer epithelial cell) .
Kaempferol-7-O-α-L-rhamnopyranoside (103) was also isolated from the antioxidative BuOH fraction of C. osmophloeum, and showed 26.9 μM and 68.1 μM of EC50 values in 1-diphenyl-2-picrylhydrazyl (DPPH) and Superoxide radical scavenging assay (NBT assay), respectively .
The antioxidant activities of compounds 41, 111-112 were screened for their antioxidative potential using β-carotenelinoleate and DPPH model systems. All of the compounds showed antioxidant and radical scavenging activities. Cinnamtannin B-1(127) showed the highest activity followed by rutin (112) and quercetin-3-O-α-L-rhamnopyranoside (111), as in the case of β-carotene antioxidant activity assay .
Four kaempferol glycosides, compounds 105-108 inhibited lipopolysaccharide (LPS) and interferon (IFN)-γ-induced nitric oxide (NO), and cytokines [tumor necrosis factor TNF-α and interleukin IL-12] in a dose-dependent manner. The concentration of 50% inhibition (IC50) of NO by compounds 105, 106, 107 were 40, 15, 20 μM, respectively. In parallel, these concentrations were approximately in a similar manner to that observed for TNF-α and IL-12 production. However, compound 109 inhibited NO and cytokines production by 30% at 100 μM concentration. On the other hand, compounds 106 and 107 showed no inhibitory effect on the production of NO from macrophages, when inducible NO synthase was already expressed by the stimulation with LPS and IFN-γ .
NF-κB Inhibitory Activity
Trans-cinnamaldehyde (20) and 2-methoxycinnamaldehyde (21) were identified as NF-κB inhibitors from C. cassia with IC50 values of 43 μM and 31 μM, respectively. As a positive control, caffeic acid phenethyl ester (CAPE) showed an IC50 value of 2 μM on NF-κB transcriptional activity. Both compounds 20 and 21 inhibited LPS–induced DNA binding activity of NF-κB in addition to NF-κB transcriptional activity .
In the course of a program to screen for tyrosinase inhibitors from plants, Ngoc et al found that a MeOH extract of the twigs of C. cassia exhibited a strong inhibitory activity (>85% inhibition at 100 μg/mL). Cinnamaldehyde and its analogues (compounds 20-25, 27, 30-32 and 47-48) showed strong inhibitory activity against tyrosinase, with IC50 values ranging from 0.24 to 0.94 mM .
In this review, we summarize the secondary metabolites reported from Cinnamomum species as well as their biological activities. All the information showed that Cinnamomum is a promising and rich source for natural products with chemical and pharmacological diversity. The competitive results stimulate us to get a better understanding of Cinnamomum species from the phytochemical and pharmacological viewpoints and to elucidate the chemical composition of substances responsible for the pharmacological activities.
This work was supported by Scientific Research Fund of Xinxiang Medical University grants [2013QN121].