Cryptomeria japonica, a commercially important tree throughout Asia and the Azores Archipelago (Portugal), is currently waste/by-products of wood processing that can be converted into eco-friendly and high added-value products, such as essential oils (EOs), with social, environmental and economic impacts.
1. Introduction
Numerous plant-derived essential oils (EOs), due to their valuable odoriferous and bioactivity properties, and GRAS (Generally Recognized as Safe) status, have applications in many fields, such as aromatherapy, cosmetic, cosmeceutical, food, beverage, household, pharmaceutical, phytomedicine and pest control. However, the bioactivity and potential commercial use of EOs depends on their complex mixture of organic compounds, produced through the secondary metabolic pathways of aromatic plants
[1][2][3][4], such as the conifer Cupressaceae family
[4].
Cryptomeria japonica (Thunb. ex L.f.) D. Don (Cupressaceae), commonly called a Japanese cedar or
sugi, is a forest tree endemic to Japan, and widely distributed in warm and cool temperate climates.
Cryptomeria is a monotypic genus that includes only one species with two recognized varieties:
C. japonica var.
japonica and
C. japonica var.
sinensis, the latter being native to China
[5].
C. japonica is a very large, conical, evergreen monoecious tree that can reach up to 70 m (230 ft) in height with a trunk diameter of up to 4 m (13 ft). It is a fast growth tree that prefers moist, deep and well-drained soils
[6]. The bark is reddish-brown, fibrous and peels off in vertical strips. The leaves are odorous due to the presence of EO and are 0.5–1 cm (0.20–0.39 in) long and needle-like in structure. The seed cones are globular up to 1–2 cm (0.39–0.79 in) in diameter with about 20–40 scales
[7].
C. japonica is one of the main plantation forest tree species in Asian countries (Japan, Korea, Taiwan, India and China) and in the Azores Archipelago (Portugal). In Azores, forests account for 31% of the land area, where
C. japonica occupies over 12,698 hectares and is the most commercially important tree species. It was introduced in Azores in the mid-19th century, where it developed very well due the similar pedological and climatic conditions to those of its original country. In Azores,
C. japonica is often planted around farms to create shelter lines, which increase pasture productivity by creating favorable microclimates for crop and livestock
[8].
2. Antimicrobial Activity of C. japonica EO in Food Industry and Human Diseases
EOs are generally accepted as natural antimicrobials and antioxidants that can be used in the food industry as bio-preservatives to increase shelf life and quality of food products
[9]. In addition, infections caused by fungi and bacteria represent a key issue due to the development of resistant species to current fungicides and antibiotics. Therefore, EOs could be an ecological and effective alternative to synthetic antimicrobial agents
[9].
Table 1 shows the antimicrobial activity of C. japonica EO from different tissues and geographical origins, against several gram-positive and gram-negative bacterial strains, as well as against various fungal species. The minimal inhibitory concentrations (MICs) were determined by the broth dilution method.
Table 1. Antimicrobial activities of Cryptomeria japonica essential oil by plant organ and country of origin.
Origin |
Plant Organ |
Target Species |
Efficiency |
Ref. |
Portugal |
Leaves, heartwood, bark |
Mycobacterium tuberculosis, Botrytis cinerea, Fusarium circinatum, Cryphonectria parasitica, Aspergillus niger, Trichoderma harzianum, Cladosporium cladosporioides, Cladosporium sp., Candida albicans, Candida tropicalis, Saccharomyces cerevisiae, Cryptococcus neoformans, Aspergillus fumigatus, Microsporum gypseum, Trichophyton rubrum, Trichophyton mentagrophytes |
Effective against M. Tuberculosis, T. harzianum, B. cinerea, C. cladosporioides and Cladosporium sp., MICs range 0.025–0.25 mg/mL |
[10] |
South Korea |
Leaves plus twigs |
Candida albicans, Candida pseudotropicalis, Candida glabrata, Candida tropicalis, Candida krusei, Candida parapsilosis, Cryptococcus neoformans, Aspergillus fumigatus |
Effective, MICs 2.18 mg/mL or higher |
[11] |
Taiwan |
Leaves, heartwood, sapwood, bark |
Trametes versicolor, Lenzites betulina, Laetiporus sulphureus, Gloeophyllum trabeum, Fusarium oxysporum, Rhizoctonia solani, Ganoderma australe, Fusarium solani, Pestalotiopsis funereal, Collectotrichum gloeosporioides |
Highly effective, IC50 range 0.039 > 0.500 mg/mL, except bark EO |
[12] |
Japan |
Heartwood |
Staphylococcus epidermis, Trichophyton rubrum |
Effective, MIC = 0.313 mg/mL, except S. epidermis |
[13] |
South Korea |
Leaves |
Staphylococcus epidermis, Propionibacterium acne |
Effective, MICs range 0.156–10 µL/mL |
[14] |
South Korea |
Leaves |
Escherichia coli, Staphylococcus aureus, Staphylococcus epidermis, Streptococcus pyogenes, Streptococcus mutans, Streptococcus sanguinis, Streptococcus sobrinus, Streptococcus ratti, Streptococcus criceti, Streptococcus anginosus, Streptococcus gordonii, Actinobacillus actinomycetemcomitans, Fusobacterium nucleatum, Prevotella intermedia, Porphylomonas gingivalis |
Effective, MICs range 0.025–12.8 mg/mL, except E. coli |
[15] |
South Korea |
Leaves plus twigs |
Escherichia coli, Enterobacter aerogenes, Enterobacter cloacae, Citrobacter freundii, Acinetobacter calcoaceticus, Staphylococcus aureus, Bacillus subtilis, Klebsiella oxytoca, Klebsiella pneumoniae, Pseudomonas aeruginosa, Serratia marcescens |
Ineffective, MICs > 21.8 mg/mL |
[11] |
Taiwan |
Leaves, heartwood, twigs, bark |
Legionella pneumophila |
Ineffective, MBC > 2 mg/mL |
[16] |
Antimicrobial compounds are usually highly correlated with antioxidant effects
[17]. In fact, besides microbial contamination, lipid peroxidation is a real problem related to food deterioration and the addition of antioxidants is an attractive strategy to retard or even stop oxidation processes.
C. japonica extracts from different tissues are rich in phenolics, which are well-known natural antioxidants and antibacterial agents
[18][19]. Contrary to
C. japonica extracts, EO from various tissues of this plant exhibited weak antioxidant activities (in 2,2-diphenyl-1-picrylhydrazyl free radical scavenging assays), presenting the sapwood EO with the best value (IC
50 = 113 μg/mL), followed by twigs, heartwood, bark and lastly leaf EOs
[20]. The effect of sapwood EO on the free radical scavenging assay is attributed to its hydrogen-donating ability, possibly due to the high content of ferruginol (an oxygenated diterpene). Thus, sapwood EO or ferruginol can also be used as natural food preservatives in food industry. In fact, it has already been reported that diterpenes show higher antioxidant and antimicrobial effects than monoterpenes
[21].
Enrichment of
C. japonica EO fractions with specific compounds can be a useful strategy to pest/microbes management, where deterpenation with vacuum fractional distillation can be effective. Kusumoto and Shibutani
[22] had submitted EO from
C. japonica leaves to an open system mild heat treatment, which decreased the content of monoterpene hydrocarbons and increased the content of oxygenated sesquiterpenes and diterpenes. They found that the evaporation residue had higher antifungal activity than the crude EO. Also, Salha et al.
[23] reported the same findings for
Origanum majorana EO. Further studies should explore this issue.
3. Acaricidal and Insecticidal Activities of C. japonica EO
The EOs play a functional role in the plant chemical defense against phytopathogens and pests
[2][24]. For that reason, they are a potentially good source of environmentally friendly pesticides or pest-control agents.
Table 2 shows the insecticidal and acaricidal effects of
C. japonica EO from different tissues.
Spider mites, such as
Tetranychus urticae and
Tetranychus kanzawai, are known as world pests of agricultural crops. However, since spider mites easily build up a tolerance to pesticides, EOs have been studied as alternative eco-pesticides. Yamashita et al.
[25] found that EO from the leaves of
C. japonica is a fruitful option to control these mites (
Table 2). They mainly attributed this acaricidal activity to the ent-kaurene compound, followed by elemol.
Silverfish
(Lepisma saccharina), another pest common in libraries and museums where paper books and labels are abundant, are insects that owe their survival to their secretive life in damp, cool places. As observed in a Wang et al.
[26] study, this pest is also sensitive to
C. japonica leaf EO, which highly repelled silverfish (>80% of repellency at 0.01 mg/cm
3 after 4 h) and killed it on contact assay (LD
50 value of 0.087 mg/cm
3 after 10 h) (
Table 2). These authors assigned these toxic effects to volatiles (monoterpenes) and non-volatiles compounds (such as ent-kaurene and elemol), respectively.
Biodegradation of wood caused by termites is one of the most serious problems for wood utilization, and extractives from wood tissues can provide natural protection against harmful pests. Therefore, and as shown in
Table 2, EO from
C. japonica (namely from leaf and heartwood) can be a natural termicide. In particular, elemol plus ent-kaurene chemotype is associated with high antitermitic activity (by contact assay), which in the Cheng et al.
[27] study was correlated with elemol and α-terpineol compounds.
It is interesting to note that EO from
C. japonica leaves is more effective in larvicidal and repellent activities against
A. aegypti and
A. albopictus than their methanolic extracts
[28][29]. However, methanolic extracts from other
C. japonica tissues (such as sapwood) have also been stated as excellent mosquito larvicidal agents
[29][30].
The larvicidal effects of C. japonica leaf EO on Anopheles gambiae (the main malaria vector), and revealed promising results in the laboratory (Table 2) and semi-field conditions.
Table 2. Insecticidal and acaricidal activities of Cryptomeria japonica essential oil from different tissues.
Plant Organ |
Pests |
Bioassay |
Efficiency |
Ref |
Leaves |
Lepisma saccharina |
Contact assay (on treated filter papers) against the adult silverfish |
Significant toxicity with LD50 of 0.087 mg/cm3 after 10 h |
[26] |
Repellent assay |
More than 80% of repellency at 10 µg/cm3 after 4 h |
Leaves |
Aedes aegypti |
Aqueous suspension of essential oil against the fourth-instar mosquito larvae |
Significant larvicidal activity with LC50 of 37.5 µg/mL after 24 h |
[31] |
Bark |
Significant larvicidal activity with LC50 of 48.1 µg/mL after 24 h |
Sapwood |
Significant larvicidal activity with LC50 of 82.7 µg/mL after 24 h |
Heartwood |
Significant larvicidal activity with LC50 of 72.0 µg/mL after 24 h |
Leaves |
Aedes albopictus |
Aqueous suspension of essential oil against the fourth-instar mosquito larvae |
Significant larvicidal activity with LC50 range of 51.2–57.9 µg/mL after 24 h |
[28] |
Leaves |
Aedes aegypti |
Repellent assay |
82% of repellency at 1.92 µg/cm3 after 20 min |
[32] |
Bark |
More than 70% of repellency at 1.92 µg/cm3 after 20 min |
Twigs |
About 70% of repellency at 1.92 µg/cm3 after 20 min |
Wood |
More than 50% of repellency at 1.92 µg/cm3 after 20 min |
Leaves |
Aedes albopictus |
Repellent assay |
71% of repellency at 1.92 µg/cm3 after 20 min |
[32] |
Bark |
More than 60% of repellency at 1.92 µg/cm3 after 20 min |
Twigs |
More than 60% of repellency at 1.92 µg/cm3 after 20 min |
Wood |
More than 60% of repellency at 1.92 µg/cm3 after 20 min |
Leaves |
Anopheles gambiae |
Aqueous suspension of essential oil against the third-instar mosquito larvae |
Significant larvicidal activity with LC50 of 40.9 µg/mL after 24 h |
[33] |
Leaves |
Coptotermes formosanus |
Contact assay (on treated filter papers) against the adult termite |
High mortality, with LD50 of 1.57 mg/g after 7 days |
[27] |
Bark |
Inactive |
[34] |
Sapwood |
Mortality of 100% with LC50 of 4.7 mg/g after 5 days |
Heartwood |
Mortality of 100% with LC50 of 2.8 mg/g after 5 days |
Leaves |
Reticulitermes chinensis |
Contact assay (on treated filter papers) against the adult termite |
High mortality, with LC50 of 0.9 µL/mL after 5 days |
[35] |
Bark |
LC50 of 19.6 µL/mL after 5 days |
Sapwood |
LC50 of 158.3 µL/mL after 5 days |
Heartwood |
High mortality, with LC50 of 1.8 µL/mL after 5 days |
Leaves |
Tetranychus kanzawai |
Contact assay (on treated leaf discs) against spider mites |
Significant mortality, with LC50 of 1109 µg/mL after 96 h |
[25] |
Leaves |
Tetranychus urticae |
Contact assay (on treated leaf discs) against spider mites |
Significant mortality, with LC50 of 1150 µg/mL after 96 h |
[25] |
Leaves |
Reticulitermes chinensis |
Contact assay (on treated filter papers) against the adult termite |
High mortality, with LC50 of 0.9 µL/mL after 5 days |
[35] |
Bark |
LC50 of 19.6 µL/mL after 5 days |
Sapwood |
LC50 of 158.3 µL/mL after 5 days |
Heartwood |
High mortality, with LC50 of 1.8 µL/mL after 5 days |
Leaves |
Tetranychus kanzawai |
Contact assay (on treated leaf discs) against spider mites |
Significant mortality, with LC50 of 1109 µg/mL after 96 h |
[25] |
Leaves |
Tetranychus urticae |
Contact assay (on treated leaf discs) against spider mites |
Significant mortality, with LC50 of 1150 µg/mL after 96 h |
[25] |
4. Other Biocidal Activities of C. japonica EO
EO from leaves of
C. japonica from Azores (α-pinene chemotype) has recently been reported to have high molluscicidal activity against
Radix peregra (Lymnaeidae), a freshwater snail that hosts a number of significant parasites, such as
Fasciola hepatica [36]. This parasite is the causing agent of fascioliasis, a well-known veterinary problem of vertebrate domestic livestock, which causes animal production losses and consequent economic costs
[37]. The lethal concentrations (LC
50) of the EO varied between 33.3 and 61.8 ppm on an aqueous suspension assay
[36]. Although the author has not assessed individual EO components for molluscicidal activity, it is worth pointing out that this EO has α-pinene as the major component. Moreover, this same EO chemotype exhibited inhibitory activities against
Pseudaletia unipuncta (Lepidoptera: Noctuidae), an important pest of agricultural crops. Particularly, this leaf EO inhibited eggs hatching and thereafter exhibited lethal and sub-lethal effects. Additionally, it showed high repellency properties against adults
[38].
More recently, some other
C. japonica bioactivities have been described. For instance, Tanaka et al.
[39] reported that chemical components of
C. japonica leaves suppress the growth of invasive plants (
Robinia pseudoacacia) and weeds (
Trifolium repens), which are the largest competitor of agricultural crops, with negative impact on productivity.
In addition, there are some studies on the growth inhibition activities of
C. japonica chemical components (mainly from bark) against harmful marine
[40] and freshwater
[18] algae. The strong growth-inhibitory activity of the
C. japonica bark EO against the bacillariophyceae
Skeletonema costatum (commonly known as red tide plankton) was correlated with the presence of ferruginol
[40], which has a strong antioxidant activity, as already mentioned. The potential of a new use for components of
C. japonica bark EO to control red tide plankton growth, a serious environmental problem in the world’s oceans, which can have an adverse impact on aquaculture.
5. Pharmacological Properties of C. japonica EO
Aromatic plants, such as
C. japonica, synthesized and emitted complex mixtures of volatile organic compounds (VOCs) in order to facilitate their growth and survival
[41][42].
The VOCs from
C. japonica have already been reported to provide relaxing and stress-relieving effects on mice
[43] and on humans
[44]. In this way,
C. japonica EO could be a useful tool in mental health management.
In addition, the most abundant VOCs emitted from
C. japonica wood during the drying process, in the wood industry, are sesquiterpenes, such as δ-cadinene, α-muurolene and β-cadinene. These VOCs were assessed as having soothing effects in a human sensory evaluation
[45]. Moreover, the main constituent of
C. japonica heartwood EO is δ-cadinene
[12][41]. It is believed that this compound and other VOCs of
C. japonica suppress the sympathetic nervous system activity in humans, especially in women, stimulating relaxing and pleasurable emotions
[46]. Furthermore, VOCs from
C. japonica leaves display antitussive effects in guinea pigs
[47] and increases the output of fluid in the respiratory tract
[48].
On the other hand, different tissues of
C. japonica also have bioactive compounds with benefits to the skin, which can have several skin health applications (inhibiting melanin production, skin ageing, antiseptic, etc.)
[21][49][50]. In particular, phytocompounds from this heartwood have been reported to possess antifungal properties in vitro against
Trichophyton rubrum, a major cause of
Tinea pedis [13]. Moreover, EO from
C. japonica leaves also showed excellent anti-inflammatory and antibacterial activities in vitro, being an attractive acne-mitigating candidate
[14]. Another recent study
[51] also stated that phytochemicals compounds from
C. japonica by-products, namely diterpenoids, can be useful in skin health.
In addition, the EO from
C. japonica leaves, namely its diterpenes, is a strong inhibitor of acetylcholinesterase activity, which could be an effective therapeutic agent for Alzheimer’s disease
[52]. Alternatively, this EO can be explored in the preventive dentistry field, as an effective inhibitor of oral bacteria
[15][53], or as an anticancer chemopreventive
[54] and antiulcer
[55] agent. The results of this last study, suggested that 4-terpineol could have gastroprotective activity.
Overall and according to the literature
[54], various parts of
C. japonica have been used in Asian folk medicine for a variety of indications, including liver ailments, and an antitussive, and for its antiulcer activities. Hence, more studies are warranted with respect to these health benefits, namely, the toxic effects.