Introduction

Cinnamomum burmannii (Nees and Nees) Blume is a cost-effective and significant evergreen tree from the Lauraceae family, widely distributed in Vietnam, Indonesia, Philippines, Myanmar, India and south of the Yangtze River in China (Yang et al. 2019). The Lauraceae family has essential ecological and economic value, particularly in the provisioning of non-timber resources. In addition, extracted oils are widely used in perfumery, food additives, and medicine (Reis-Avila and Oliveira 2017). Cinnamomum is regarded as one of the most commercially valuable genera among the Lauraceae family owing to the abundance of volatile oils (Jayaprakasha and Rao 2011). Essential oils are complex mixtures of natural compounds produced by plant metabolism and are responsible for the distinctive aroma of the plants (Pavela 2015). Over the past decades, essential oils derived from many medicinal plant species have been analyzed for their chemical components and prominent biological activities (Dra et al. 2017; Osanloo et al. 2017; Nascimento et al. 2018). The bark of C. burmannii has been used to treat rheumatism, diarrhea and abdominal pain in Chinese medicine (Tan et al. 2011). The roots, bark, and leaves of this plant can be used to extract aromatic oils or pigments that are widely used in the spice and pharmaceutical industries (Shan et al. 2007; Huang et al. 2011). In the meantime, C. burmannii is environmentally friendly and is also good for human health, as C. burmannii has long been used as a precious perfume material (Wang et al. 2019). In the previous phytochemical investigations, cinnamaldehyde, eugenol, coumarin, citronellol, borneol, eucalyptol and various alkenes have been identified from the essential oils derived from the leaves and stems of C. burmannii (Liu et al. 2007; Wang et al. 2009; AI-Dhubiab 2012; Li et al. 2016; Kumar and Kumari 2019). However, most of the essential oils tested in the previous studies were extracted from the C. burmannii leaves and bark. The chemical composition and characterizations of volatile oils from the fruits of C. burmannii have not been studied.

The fruits of C. burmannii can also be potentially used as a source of pigments for the exploitation of neoteric dyes (Tan et al. 2011). Surprisingly, fungal infection of fruits has rarely attracted attention, compared to the detailed studies on leaves, twigs and stems of Cinnamomum (Liu and Xu 2014; Shan et al. 2014; Jiang and Kirschner 2016). Powdery-fruit disease is a common and severe fruit disease of C. burmannii, C. cassia and C. camphora, and the pathogen can vary widely in different hosts (Chen et al. 2013; Shan et al. 2014). Previous reports have shown that powdery-fruit disease of C. burmannii and C. camphora was caused by the plant pathogenic fungus Clinoconidium cinnamomi and Clinoconidium sawadae, respectively (Jiang and Kirschner 2016). The plant pathogenic fungus Clinoconidium cinnamomi was first described as Elaeodema cinnamomi, while C. sawadae was firstly recorded as Exobasidium sawadae (Guo et al. 1991). Fruits of Cinnamomum species were mainly infected by Elaeodema and Exobasidium species, which occurred in East Asia. These pathogen species were not conspecific, and the differentiation was spore production. The spores were produced by basidia in Exobasidium and hyphae in Elaeodema. In addition, Elaeodema is an endemic genusin China (Guo et al. 1991). Taking these perplexing literature reports into consideration, it is important to reinvestigate the taxonomic affiliations by sampling different types of infected fruits of C. burmannii for further analysis.

To the best of our knowledge, the distinction of the volatile oils between normal and infected fruits of C. burmannii has not been studied. In addition, there are only a few reports on the pathogen of powdery-fruit disease of C. burmannii. This study focuses on identifying the pathogen and investigating the compositions of the volatile oils derived from the leaves and normal and infected fruits of C. burmannii, aiming to reveal the effects of powdery-fruit disease on the fruits of C. burmannii.

Materials and Methods

Plant material

Fresh leaves and normal and infected fruits of C. burmannii (2 kg) were collected from Huolu Mountain, Guangzhou, China, in November 2018, and the ripe spores were collected from the same spots in March 2019. The voucher specimens were deposited in the College of Forestry and Landscape Architecture, South China Agricultural University. The leaves and normal and infected fruits were stored at −20°C before use.

Morphological identification

The identification of the pathogen causing powdery-fruit disease was performed by observing morphological characters such as macroscopic traits of the infected fruits and the microscopic appearance of spores (Guo et al. 1991).

Fig. 1: The outward appearance of powdery-fruit disease in C. burmannii. (a) Normal and infected fruits in the growing condition. (b) Collected normal fruits. (c) Collected infected fruits

Fig. 2: Morphological characteristics of the spores

DNA extraction, NS-rDNA amplification and sequence analysis

Fresh spore samples 50–100 mg in size were harvested from the fresh infected fruits and were used for genomic DNA extraction. The genomic DNA extraction, polymerase chain reaction and sequencing of internal transcribed spacer (ITS, primer ITS 1: 5'-TCCGTAGGTGAACCTGCGG-3'; primer ITS 4: 5'-TCCTCCGCTTATTGATATGC-3') and 18S rDNA sequences (primer NS1: 5'-GTATCATATGCTTGTCTC-3'; primer NS8: 5'-TCCGCAGGTTCACCTACGGA-3') from the infected fruits were operated as described in procedures from our previous reports (Shan et al. 2019). The sequences were first edited by the BLASTN program against the database (NCBI), and were then submitted to GenBank to obtain the accession numbers.

Phylogenetic analysis

To construct a phylogeny of the pathogen, we retrieved sequences of the close hits from the NCBI (http://www.ncbi.nlm.nih.gov/) and performed multiple sequence alignment using Clustal W. The aligned files were then exported in mega format. A neighbor-joining tree was constructed in MEGA 6.0 using default parameters and bootstrap values calculated from 1,000 replications (Shan et al. 2019).

Preparation of theessential oils

The volatile oils of leaves and normal and infected fruits were isolated by hydro-distillation using a Clevenger-type apparatus for 6 h at 100°C. Distillates were further extracted with diethyl ether, and extractions were dried over anhydrous sodium sulfate, followed by filtration. All the essential oils were stored at 4°C in sealed dark glass vials for further use (Shan et al. 2016).

Essential oils analysis

The chemical composition of the volatile oils was analyzed by GC-MS according to Shan et al. (2016). Identical column and conditions were used for both GC and GC-MS. The components were indicated by comparison of their mass with NIST 2011 library data. The relative amount (RA) of each individual component from the volatile oils was expressed as the percentage of the peak area corresponding to the total peak area.

Results

Morphological identification and characterization of powdery-fruit disease pathogeny

The outward appearances of normal and infected fruits were shown in Fig. 1. The infected fruits displayed as woolen, flat spherical or irregular flat spherical shape, with diameters reaching 1.0 ~ 2.5 cm. The fruits of C. burmannii transformed into galls with reddish-brown, slightly scaly skin that fractured and peeled off, releasing buff ochre masses of spores when they were mature. During the process, the core was still the host organization. Interestingly, the powdery-fruit disease only affects the fruits of C. burmannii. Coincidentally, the time when the pathogen spores become mature is identical to C. burmanni flowering. Therefore, it is suspected that the pathogen spores probably invade the host through the flowers.

The spores shown in Fig. 2 were long ellipsoidal or oval, unicellular, and pistac with several hyaline oil globules. The spores measured up to 11.6 to 15.2 μm long and 5.2 to 8.1 μm wide (n = 30).

Molecular identification and phylogenetic analysis

From the amplification of the 18S rDNA region, an approximately 2, 071-bp PCR product was obtained for the pathogen CBd1. The sequence of the pathogen CBd1 was uploaded to GenBank, with accession number MH378887.

For phylogenetic analysis, a total of nineteen sequences among four type strains were obtained from GenBank. The 18S rDNA (NS) sequence was used to construct the phylogenetic tree. The phylogenetic tree revealed that the pathogen CBd1 formed a clade with members of the genus Acaromyces (Fig. 3). Acaromyces ingoldii (accession number NG061199) was a type strain of Acaromyces sp. and the pathogen CBd1 sequence had 99.63% similarity with the Acaromyces ingoldii sequence (accession number NG061199 and KP866248).

Essential oil analysis

By hydro-distillation, the isolated yields of the volatile oils from the fresh leaves and fruits of both normal and infected of C. burmannii were 0.160, 0.084 and 0.044% (w/w), respectively. These results revealed that the content of essential oil in leaves was significantly higher than that in fruits, with the content in normal fruits being nearly 2-fold that of infected fruits. The results data from GC-MS analysis were shown in Table 1. The chemical components of the essential oils from three different samples indicated significant variations in type and quantity. To evaluate leaf oil, at least sixty-four compounds were authenticated, which accounted for 96.20% of the total contents. Twenty-eight compounds were identified from the volatile oil of normal fruits, in contrast to fifty-two compounds in infected fruits, which constituted 89.33 and 91.48% of the total oils, respectively. These results indicated that the numbers of chemical components in infected fruits were almost twice those from normal fruits.

Additionally, the types and relative percentages of chemical components in the three essential oils also vary greatly. Borneol (24.99%), D-limonene (11.16%), L-(-)-borneol (10.51%), α-pinene (4.73%), bornyl acetate (4.56%), terpineol (3.66%) and β-pinene (3.18%) were major components in the leaf oil, with a total percentage of 62.79%. α-Caryophyllene (32.94%), L-caryophyllene (17.75%), 1, 5, 5, 8-tetramethyl-3, 7-cycloundecadien-1-ol (5.83%), epizonarene (4.82%), caryophyllene oxide (4.63%) and o-menth-8-ene (4.42%) were major components in normal fruits, with a total percentage of 70.39%. In contrast, in infected fruits, the major components were β-guaiene (10.01), (-)-β-cadinene (8.64%), l-caryophyllene (5.78%), pinene (5.68%) and α-caryophyllene (5.25%), with a total percentage of 35.36% in the oils. β-Guaiene was the most abundant ingredient in infected fruits and no other components were above 10%. Other components were present at less than 4% in infected fruits.

In addition, four common components, D-limonene, l-caryophyllene, α-caryophyllene and δ-cadinene were found in all the three essential oils. Peruviol was detected in both leaves and normal fruits but not in infected fruits. Ten common constituents were found in both normal and infected fruits: D-limonene, l-caryophyllene, α-caryophyllene, epizonarene, γ-selinene, δ-cadinene, 10s,11s-himachala -3(12), 4-diene, (+) -α-elemene, β-guaiene and longifolene, though they were variable in contents. For example, the relative content of α-caryophyllene in normal fruits was 32.94%, while that in infected fruits was 5.25%. In addition, l-caryophyllene accounted for 17.75% in normal fruits and 5.78% in infected fruits. Oppositely, the relative content of D-limonene, γ-selinene, δ-cadinene, 10s, 11s-himachala -3 (12), 4-diene, (+) -α-elemene and β-guaiene were richer in infected fruits.

Discussion

A distinct mycelium is an important characteristic of a pathogen. Unfortunately, it was challenging to obtain the CBd1pathogen from Basidiomycota since it cannot be cultured on an artificial medium. Multigene sequencing has

Table 1: Chemical compositions of the essential oils from the leaves, normal and infected fruits of C. burmannii

No.	Compound	Molecular formula	Peak area (%)
			Leaves	Normal fruits	Infected fruits
1	3-Thujene	C10H16	0.76	‒^a	‒
2	α-Pinene	C10H16	4.73	‒	5.68
3	Camphene	C10H16	2.95	‒	1.93
4	Sabenene	C10H16	0.50	‒	‒
5	(E)-1,1-Dimethyl-2-(3-methylbuta-1,3-dien-1-yl) cyclopropane	C10H16	‒	‒	0.49
6	β-Pinene	C10H16	3.18	‒	‒
7	Myrcene	C10H16	2.41	‒	0.22
8	α-Phellandrene	C10H16	1.71	‒	‒
9	p-Cymol	C10H14	‒	‒	0.47
10	α-Terpinene	C10H16	0.14	‒	‒
11	D-Limonene	C10H16	11.16	0.21	2.10
12	Eucalyptol	C10H18O	2.08	‒	1.21
13	Salicylic aldehyde	C7H6O2	0.19	‒	‒
14	Ocimene	C10H16	0.21	‒	0.14
15	γ-Terpinene	C10H16	0.84	‒	‒
16	Terpinolene	C10H16	1.85	‒	‒
17	Cyclohexene, 3-methyl-6-(1-methylethylidene)-	C10H16	‒	‒	0.35
18	Linalool	C10H18O	0.86	‒	‒
19	Fenchol	C10H18O	‒	‒	0.52
20	(+)-2-bornanone	C10H16O	0.88	‒	‒
21	Borneol	C10H18O	24.99	‒	0.81
22	L-(-)-Borneol	C10H18O	10.51	‒	‒
23	(-)-4-Terpineol	C10H18O	0.68	‒	‒
24	α-Terpinylisovalerate	C15H26O2	‒	0.14	‒
25	2-(4-Methylphenyl)propan-2-ol	C10H14O	0.09	‒	‒
26	Terpineol	C10H18O	3.66	‒	‒
27	Decanal	C10H20O	0.27	‒	‒
28	Octyl acetate	C10H20O2	0.18	‒	‒
29	α-Bornene	C10H16	‒	‒	2.96
30	(z)-3,7-dimethylocta-2,6-dienal	C10H16O	0.06	‒	‒
31	Geraniol	C10H18O	1.23	‒	‒
32	Citral	C10H16O	0.09	‒	‒
33	2,4,6-Trimethyl-1,3,6-heptatriene	C10H16	‒	‒	0.11
34	1-Decanol	C10H22O	0.35	‒	‒
35	Bornyl acetate	C12H20O2	4.56	‒	0.37
36	γ-Pyronene	C10H16	0.83	‒	‒
37	Isoterpinolene	C10H16	‒	‒	0.32
38	Neryl acetate	C12H20O2	0.23	‒	‒
39	1, 2-Dimethylspiro [4.4]nona-1, 3-diene	C11H16	‒	0.26	‒
40	Ylangene	C15H24	0.18	‒	‒
41	Clovene	C15H24	‒	0.29	‒
42	α-Copaene	C15H24	0.19	‒	‒
43	Isolongifolene	C10H16	‒	‒	0.27
44	Geranyl acetate	C12H20O2	0.87	‒	‒
45	α-Funebrene	C15H24	-	‒	0.55
46	(-)-β-Elemene	C15H24	0.19	‒	‒
47	3-Acetyl-4-ethenylphenyl acetate	C12H12O3	‒	‒	0.24
48	Cyclodecane	C10H20	0.08	‒	‒
49	l-Caryophyllene	C15H24	2.81	17.75	5.78
50	Calarene	C15H24	0.10	‒	‒
51	1H-Benzocycloheptene,2,4a,5,6,7,8-hexahydro-3,5,5,9-tetramethyl-, (4aR)-	C15H24	‒	0.19	‒
52	Coumarin	C9H6O2	0.47	‒	‒
53	Isoledene	C15H24	0.09	‒	2.62
54	(+)-Aromadendrene	C15H24	0.45	‒	‒
55	Cinnamyl acetate	C15H24	1.35	‒	‒
56	β-Copaene	C15H24	‒	0.57	‒
57	α-Caryophyllene	C15H24	0.67	32.94	5.25
58	a-Gurjunene	C15H24	0.10	‒	‒
59	α-Guaiene	C15H24	‒	‒	0.15
60	Alloaromadendrene	C15H24	0.14	‒	‒
61	trans-Calamenene	C15H22	-	‒	0.41
62	γ-Muurolene	C15H24	0.28	‒	‒
63	3,4-Dihydrocoumarin, 4,4-dimethyl-6-ethyl-	C13H16O2	‒	0.20	‒
64	Germacrene D	C15H24	0.20	‒	‒
65	Cedrene-V6	C15H24	‒	‒	1.16

Table 1: Continued

66	β-Eudesmene	C15H24	0.10	‒	‒
67	2-Isopropenyl-4a,8-dimethyl-1,2,3, 4,4a,5,6,7-octahydronaphthalene	C15H24	‒	1.55	‒
68	Epizonarene	C15H24	‒	4.82	1.85
69	(-)-β-Cadinene	C15H24	‒	‒	8.64
70	Azulene,1,2,3,3a,4,5,6,7-octahydro-1,4-dimethyl-7-(1-methylethenyl)-, (1R,3aR,4R,7R)	C15H24	‒	‒	3.17
71	(+)-Valencene	C15H24	‒	0.58	‒
72	δ-Selinene	C15H24	0.15	‒	‒
73	(-)-α-Selinene	C15H24	‒	2.73	‒
74	γ-Selinene	C15H24	‒	1.38	2.97
75	Bicyclogermacrene	C15H24	1.74
76	α-Gurjunene	C15H24	0.12	‒	3.29
77	(-)-γ-Cadinene	C15H24	0.06
78	δ-Cadinene	C15H24	0.19	0.17	0.36
79	Naphthalene,1,2,4a,5,6,8a-hexahydro-4,7-dimethyl-1-(1-methylethyl)-	C15H24	‒	0.66	‒
80	1-tert-Butyl-3,5-dimethylbenzene	C12H18	‒	‒	1.00
81	Alloaromadendrene	C15H24	‒	‒	0.79
82	Eudesma-3,7(11)-diene	C15H24	‒	‒	0.42
83	α-Farnesene	C15H24	‒	0.28	‒
84	Neoisolongifolene	C15H24	‒	‒	0.29
85	Calarene	C15H24	‒	‒	0.81
86	α-Elemol	C15H26O	0.21	‒	‒
87	Peruviol	C15H26O	0.35	1.02	‒
88	Eudesma-3,7(11)-diene	C15H24	0.20	‒	‒
89	β-Neoclovene	C15H24	‒	‒	0.63
90	Caryophyllenyl alcohol	C15H26O	‒	‒	3.26
91	β-Patchoulene	C15H24	‒	‒	0.52
92	Espatulenol	C15H24O	0.43	‒	‒
93	Aromadendrene oxide-(1)	C15H24O	‒	‒	0.88
94	Caryophyllene oxide	C15H24O	‒	4.63	‒
95	6-Isopropyl-4,8α-dimethyl-1,2,3,7,8,8α-hexahydronaphthalene	C15H24	‒	‒	3.45
96	β-Vatirenene	C15H24	‒	‒	0.52
97	10s,11s-Himachala-3(12),4-diene	C15H24	‒	0.40	2.01
98	Cycloheptane, 4-methylene-1-methyl-2-(2-methyl-1-propen-1-yl)-1-vinyl-	C15H24	‒	‒	0.91
99	1,5,5,8-Tetramethyl-3,7-cycloundecadien-1-ol	C15H26O	‒	5.83	‒
100	(-)-Globulol	C15H26O	0.70	‒	‒
101	(+)-Viridiflorol	C15H26O	0.38	‒	‒
102	(+)-α-Elemene	C15H24	‒	0.97	3.01
103	5-Cyclohexyl-1-pentene	C11H20	‒	‒	0.92
104	Tetradecanal	C14H28O	0.13	‒	‒
105	o-Menth-8-ene	C10H18	‒	4.42	‒
106	Machilol	C15H26O	0.24	‒	‒
107	γ-Maaliene	C15H24	‒	‒	0.84
108	Spathulenol	C15H24O	0.28	‒	‒
109	β-Guaiene	C15H24	‒	2.35	10.01
110	β-Eudesmol	C15H26O	0.16	‒	‒
111	α-Eudesmol	C15H26O	0.28	‒	‒
112	γ-Eudesmol	C15H26O	‒	‒	2.11
113	Isocamphane	C10H18	‒	1.62	‒
114	Naphthalene, 1,2,4a,5,8,8a-hexahyd ro-4,7-dimethyl-1-(1-methylethyl)- , (1α,4a β,8aα)-(. +/-.)-	C15H24	‒	‒	2.29
115	Eudesm-7(11)-en-4-ol	C15H26O	‒	1.46	‒
116	1H-Cyclopropa[a]naphthalene, decahydro-1,1,3a-trimethyl-7-methylene-, [1aS-(1aα,3aα,7aβ,7bα)]-	C15H24	‒	‒	1.52
117	Longifolene	C15H24	‒	1.34	0.44
118	Nerolidol	C15H26O	‒	0.57	‒
119	(E)-β-Farnesene	C15H24	‒	‒	0.46
120	Phytol	C20H40O	0.13	‒	‒

a: not detected (< 0.1%)

been commonly used for the identification of species level. In this study, the primers pair ITS 1 and ITS 4 and NS 1 and NS 8 were selected to amplify the internal transcribed spacer region of the ribosomal RNA. Unfortunately, the sequence based on the primers ITS 1 and ITS 4 was not successfully acquired, consistent with a literature report (Jiang and Kirschner 2016). Jiang and Kirschner (2016) reported that powdery-fruit disease of C. burmannii was caused by the fungus C. cinnamomi based on the morphological characters and partial nuclear ribosomal large subunit RNA (LSU) gene sequencing data. In our work, the pathogen CBd1was shown to maintain 99.63% sequence similarity to that of Acaromyces ingoldii (accession number NG061199 and KP866248) according to the morphological characteristics and 18S rDNA (NS) gene sequence. Multigene sequencing will be necessary to accurately identify the species in the future.

Fig. 3: Molecular phylogenetic analysis of pathogen CBd1 with nineteen strains obtained from GenBank. The tree was constructed by the neighbor-joining method based on 18S rDNA (NS) sequences. Bootstrap values after 1000 replicates were expressed as percentages at branching points

Essential oils are complicated mixtures of natural products consisting of aromatic volatile components such as hydrocarbons, lipids, phenols, terpenes, ketones and their derivatives, showing various biological activities such as anti-inflammatory, antimicrobial, anti-proliferative and insecticidal properties (Taga et al. 2012; Sharifi-Rad et al. 2017). There have been many reports about the composition of essential oils from the leaves and bark of C. burmannii. The chemical profile of essential oil from the leaves of C. burmannii growing in Kunming (China) was mainly composed of linalool (54.93%) (Ding et al. 1994). Interestingly, trans-cinnamaldehyde (60.17%), eugenol (17.62%), coumarin (13.39%) and borneol (6.79%) were the major volatile components in the leaf oil of C. burmannii collected from Guangzhou, China (Wang et al. 2009). Thirty-three compounds were obtained from the leaf essential oil of C. burmannii by supercritical CO₂ extraction technology, and among them, borneol (47.23%) was the predominant volatile component (Li et al. 2016). In this study, we found that borneol (24.99%), D-limonene (11.16%) and L-(-)-borneol (10.51%) were the major components with borneol being the most abundant compound in the leaf oil. Overall, borneol existed in all the samples, while the relative amount of this component varied greatly. Such variability in different specimens could be related to geographical locations. In addition, the chemical compositions also varied by a large extent in different plant organs. For example, coumarin was the most abundant compound in the C. burmannii bark, while borneol was the predominant compound in the leaves (Wang et al. 2013). The bark oil of C. burmannii from Guangxi (China) was rich in eucalyptol (30.93%) and borneol (18.31%) (Li et al. 2015). To the best of our knowledge, there is no report analyzing the fruit essential oils of C. burmannii, and only one study has shown that eucalyptol, α-terpineol, α-phellandrene, D-limonene, α-pinene and β-pinene were the main components in the fruit oil of C. migao, which is in the same genus as C. burmannii (Zhang et al. 2011). We found that α-caryophyllene (32.94%) and l-caryophyllene (17.75%) were the main components, with a negligible amount of D-limonene (0.21%) in normal fruits. In contrast, a lower content of α-pinene (5.48%) and a higher content of D-limonene (2.10%) were found in the infected fruits. Overall, the chemical composition of essential oils not only correlates to plant species and organs, but also to the growth environment and extraction methods and techniques. These factors are responsible for the deviations in the oil components in terms of quality and quantity (Wang et al. 2019). It should be noted that the chemical composition and percentage differences between the normal and infected fruits may relate to the production of phytotoxic substances by the pathogen (Shan et al. 2012; Sun et al. 2017; Meng et al. 2019). The potential chemical structures and biological activities of the phytotoxins due to pathogen infection will be studied in the future.

Conclusion

The 18S rDNA (NS) gene sequence of the pathogen CBd1 (accession number MH378887) exhibited 99.63% similarity to that of Acaromyces ingoldii (accession numbers NG061199 and KP866248). The compositions and ratios of the essential oils from normal and infected fruits of C. burmannii varied greatly. The differences could be attributed to the pathogen infection in the fruits of C. burmannii, although the mechanism remains unknown, which will require further exploration.

Acknowledgments

We thank Huixiong Wu for logistical assistance. This research was co-financed by the National Project of Standardization on Chinese Materia Medica-standard of Cinnamomum cassia (ZYBZH-Y-GD-13), the Distinguished Young Scientist Starting Grant of Guangdong Province (2017KQNCX016), the Forestry Science and Technology Innovation Project of Guangdong Province (2020KJCX004) and the Standardized cultivation of C. cassia (TR-0080-2018).

References

AI-Dhubiab BE (2012). Pharmaceutical applications and phytochemical profile of Cinnamomum burmannii. Pharmacogn Rev 6:125–131

Chen H, H Chen, Z Liu, T Huang, Y Chen (2013). Study on integrated control the powdery-fruit disease of Cinnamomum cassia. Nat Sci J Harbin Norm Univ 29:72–76

Ding J, X Yu, Z Ding, B Cheng, Y Yi, W Yu, N Hayashi, H Komae (1994). Essential oils of some Lauraceae species from the southwestern parts of China. J Essent Oil Res 6:577–585

Dra LA, MAS Brahim, B Boualy, A Aghraz, M Barakate, S Oubaassine, M Markouk, M Larhsini (2017). Chemical composition, antioxidant and evidence antimicrobial synergistic effects of Periploca laevigata essential oil with conventional antibiotics. Indust Crop Prod 109:746–752

Guo L, YL Zhou, YB Li (1991). Study of the genus Elaeodema and Exobasidium sawadae. Acta Mycol Sin 10:31–35

Huang S, Y Pan, D Gan, X Ouyang, S Tang, SINE Kunwe, H Wang (2011). Antioxidant activities and UV-protective properties of melanin from the berry of Cinnamomum burmannii and Osmanthus fragrans. Med Chem Res 20:475–481

Jayaprakasha GK, LJM Rao (2011). Chemistry, biogenesis, and biological activities of Cinnamomum zeylanicum. Crit Rev Food Sci 51:547–562

Jiang MG, R Kirschner (2016). Unraveling two East Asian species of Clinoconidium (Cryptobasidiaceae). Mycoscience 57:440–447

Kumar S, R Kumari (2019). Cinnamomum: Review article of essential oil compounds, ethnobotany, antifungal and antibacterial effects. Open Access J Sci 3:13–16

Li H, R Xu, G Guo, C Liu (2016). GC-MS analysis of volatile oil by supercritical CO₂ extraction from Cinnamomum burmannii leaves. Food Res Dev 37:135‒138

Li X, Y Chen, T Zhou (2015). GC-MS analysis of volatile oil from the bark of Zhuang Ethnic Medicine Cinnamomum burmannii. J Chin Med Mater 38:548–549

Liu Y, F Xu (2014). A combination of morphological and molecular analyses to distinguish two fungal pathogens causing leaf spots on Cinnamomum burmannii. For Pathol 44:382–386

Liu Y, H Wang, X Lu (2007). Analysis and comparison of the volatile oil from the stems and leaves of Cinnamomum burmanii (Nees) BI. By GC-MS. Lishizhen Med Mater Med Res 18:2383–2385

Meng J, G Gu, P Dang, X Zhang, W Wang, J Dai, Y Liu, D Lai, L Zhou (2019). Sorbicillinoids from the fungus Ustilaginoidea virens and their phytotoxic, cytotoxic, and antimicrobial activities. Front Chem 7; Article 435

Nascimento KFD, FMF Moreira, JA Santos, CAL Kassuya, JHR Croda, CAL Cardoso, MC Vieira, ALTG Ruiz, MA Foglio, J ED Carvalho, ASN Formagio (2018). Antioxidant, anti-inflammatory, antiproliferative and antimycobacterial activities of the essential oil of Psidium guineense Sw. and spathulenol. J Ethnopharmacol 210:351–358

Osanloo M, A Amani, H Sereshti, MR Abai, F Esmaeili, MM Sedaghat (2017). Preparation and optimization nano-emulsion of Tarragon (Artemisia dracunculus) essential oil as effective herbal larvicide against Anopheles stephensi. Indust Crop Prod 109:214–219

Pavela R (2015). Acute toxicity and synergistic and antagonistic effects of the aromatic compounds of some essential oils against Culex quinquefasciatus Say larvae. Parasitol Res 114:3835–3853

Reis-Avila G, JM Oliveira (2017). Lauraceae: a promising family for the advance of neotropical dendrochronology. Dendrochronologia 44:103‒116

Shan B, YZ Cai, JD Brooks, H Corke (2007). Antibacterial properties and major bioactive components of cinnamon stick (Cinnamomum burmannii): activity against foodborne pathogenic bacteria. J Agric Food Chem 55:5484–5490

Shan T, H Feng, Y Xie, C Shao, J Wang, Z Mao (2019). Endophytic fungi isolated from Eucalyptus citriodora Hook. f. and antibacterial activity of crude extracts. Plant Prot 45:149–155

Shan T, X Tang, Y Liu, W Wang, X Chen, Z Duan, H Wu, J Wang (2016). Chemical compositions and antibacterial activities of volatile oils from Taxodium ascendens leaves and cones. J South Chin Agric Univ 37:72–76

Shan T, H Feng, C Ai, S Sun, J Wang (2014). Review on diseases of Cinnamomum camphora (L.) Presl and their control. Hunan For Sci Technol 41:75–77

Shan T, W Sun, H Liu, S Gao, S Lu, M Wang, Z Chen, S Wang, L Zhou (2012). Determination and analysis of ustiloxins A and B by LC-ESI-MS and HPLC in false smut balls of rice. Intl J Mol Sci 13:11275–11287

Sharifi-Rad J, A Sureda, GC Tenore, M Daglia, M Sharifi-Rad, M Valussi, R Tundis, M Sharifi-Rad, MR Loizzo, AO Ademiluyi, R Sharifi-Rad, SA Ayatoliahi, M Iriti (2017). Biological activities of essential oils: from plant chemoecology to traditional healing systems. Molecules 22:1-55

Sun W, A Wang, D Xu, W Wang, J Meng, J Dai, Y Liu, D Lai, L Zhou (2017). New ustilaginoidins from rice false smut balls caused by Villosiclava virens and their phytotoxic and cytotoxic activities. J Agric Food Chem 65:5151–5160

Taga I, CQ Lan, I Altosaar (2012). Plant essential oils and mastitis disease: their potential inhibitory effects on pro-inflammatory cytokine production in response to bacteria related inflammation. Nat Prod Commun 7:675–682

Tan M, D Gan, L Wei, Y Pan, S Tang, H Wang (2011). Isolation and characterization of pigment from Cinnamomum burmannii peel. Food Res Intl 44:2289–2294

Wang R, RJ Wang, B Yang (2009). Extraction of essential oils from five cinnamon leaves and identification of their volatile compound compositions. Innov Food Sci Emerg 10:289–292

Wang Y, LT Zhang, YX Feng, D Zhang, SS Guo, X Pang, ZF Geng, C Xi, SS Du (2019). Comparative evaluation of the chemical composition and bioactivities of essential oils from four spice plants (Lauraceae) against stored-product insects. Indust Crop Prod 140:111640

Wang YH, B Avula, ND Nanayakkara, JP Zhao, IA Khan (2013). Cassia cinnamon as a source of coumarin in cinnamon-flavored food and food supplements in the United States. J Agric Food Chem 61:4470‒4476

Yang Y, Y Song, P Xin (2019). The chloroplast genome of aromatic plants Cinnamomum burmannii (Lauraceae). Mitochondr DNA B 4:3616‒3617

Zhang XB, T Zhou, LP Guo, LQ Huang, WK Jiang, ZN Yang, CY Ma (2011). Volatile oil contents correlate with geographical distribution patterns of the Miao Ethnic herb Fructus cinnamomi. Acta Ecol Sin 31:5299–5306