Volatile components in the essential oil of wild oregano (Coleus amboinicus Lour.)

Encapsulation of wild oregano, Plectranthus amboinicus (Lour.) Spreng, phenolic extract in baker's yeast for the postharvest control of anthracnose in papaya

BACKGROUND

Anthracnose caused by Colletotrichum gloeosporioides is considered as a major postharvest disease affecting many fruits. This plant disease is traditionally managed with synthetic fungicides, which are generally toxic and are linked to pathogen resistance. Recently, microencapsulated bioactives have been developed as potential alternative strategies to these methods, while utilizing natural fungicides and other phytochemicals. Wild oregano, Plectranthus amboinicus (Lour.) Spreng, contains potent antimicrobial phenolics, but these compounds are volatile and relatively unstable, which limits their efficacy during application. Herein, a baker's yeast microencapsulation system was applied to improve the stability of wild oregano phenolic extract (WOPE) and enhance its antifungal activity against anthracnose.

RESULTS

Encapsulation of WOPE in plasmolyzed yeast cells afforded a high encapsulation efficiency (93%) and yielded WOPE-loaded yeast microcapsules (WLYMs) with an average diameter of 2.65 μm. Storage stability studies showed WLYMs are stable for at least 4 months. A 24  -h in vitro release experiment showed that WLYMs had an initial burst release upon redispersion in water, followed by a controlled release to about 80% of the loaded WOPE. Upon application as a spray-type postharvest treatment for papaya, WLYMs exhibited a significantly improved mycelial inhibitory action against C. gloeosporioides and greatly reduced the anthracnose symptoms in papaya fruits.

CONCLUSION

This study presented a yeast microencapsulation system that can effectively stabilize WOPE and enhance its antifungal activity, making this microparticle formulation a promising environmentally safe postharvest treatment option to combat anthracnose symptoms in papaya fruits. © 2022 Society of Chemical Industry.

COVID-19: Is There Evidence for the Use of Herbal Medicines as Adjuvant Symptomatic Therapy?

BACKGROUND

Current recommendations for the self-management of SARS-Cov-2 disease (COVID-19) include self-isolation, rest, hydration, and the use of NSAID in case of high fever only. It is expected that many patients will add other symptomatic/adjuvant treatments, such as herbal medicines.

AIMS

To provide a benefits/risks assessment of selected herbal medicines traditionally indicated for "respiratory diseases" within the current frame of the COVID-19 pandemic as an adjuvant treatment.

METHOD

The plant selection was primarily based on species listed by the WHO and EMA, but some other herbal remedies were considered due to their widespread use in respiratory conditions. Preclinical and clinical data on their efficacy and safety were collected from authoritative sources. The target population were adults with early and mild flu symptoms without underlying conditions. These were evaluated according to a modified PrOACT-URL method with paracetamol, ibuprofen, and codeine as reference drugs. The benefits/risks balance of the treatments was classified as positive, promising, negative, and unknown.

RESULTS

A total of 39 herbal medicines were identified as very likely to appeal to the COVID-19 patient. According to our method, the benefits/risks assessment of the herbal medicines was found to be positive in 5 cases (Althaea officinalis, Commiphora molmol, Glycyrrhiza glabra, Hedera helix, and Sambucus nigra), promising in 12 cases (Allium sativum, Andrographis paniculata, Echinacea angustifolia, Echinacea purpurea, Eucalyptus globulus essential oil, Justicia pectoralis, Magnolia officinalis, Mikania glomerata, Pelargonium sidoides, Pimpinella anisum, Salix sp, Zingiber officinale), and unknown for the rest. On the same grounds, only ibuprofen resulted promising, but we could not find compelling evidence to endorse the use of paracetamol and/or codeine.

CONCLUSIONS

Our work suggests that several herbal medicines have safety margins superior to those of reference drugs and enough levels of evidence to start a clinical discussion about their potential use as adjuvants in the treatment of early/mild common flu in otherwise healthy adults within the context of COVID-19. While these herbal medicines will not cure or prevent the flu, they may both improve general patient well-being and offer them an opportunity to personalize the therapeutic approaches.

Antimildew Effects of Plectranthus amboinicus Leaf Essential Oil on Paper

In this study, we evaluated the antimildew effects on paper of Plectranthus amboinicus (Lour.) Spreng leaf essential oil prepared through hydrodistillation. The oil was isolated with a Clevenger-type apparatus and then characterized through gas chromatography with flame ionization detection (GC-FID) and gas chromatography-mass spectrometry (GC-MS). A total of 43 compounds were identified, representing 99.5% of the oil. The main ingredients were carvacrol (50.0%), γ-terpinene (13.1%), and β-caryophyllene (11.3%). The leaf oil had excellent antimildew effects; its minimum inhibitory concentration (MIC) values against Aspergillus clavatus, A. niger, Cladosporium cladosporioides, Chaetomium globosum, Myrothecium verrucaria, Penicillium citrinum, and Trichoderma viride were 100, 200, 75, 75, 100, 150, and 150 μg/cm2 respectively. The leaf oil was further partitioned into 6 derivative fractions (PO1-PO6). PO2 had excellent antimildew effects on the abovementioned strains; at a concentration of 100 μg/cm2, all were 100% inhibited, except A. niger, which was 75.8% inhibited. Carvacrol, the main ingredient of PO2, was then isolated and used for antimildew tests; carvacrol had excellent antimildew activities. Since both P. amboinicus leaf essential oil and carvacrol were proved to have excellent antimildew effects on paper, they are worth further research and development.

Coleus aromaticus: a therapeutic herb with multiple potentials

The herb Coleus aromaticus belonging to Lamiaceae family and Coleus genus is known by numerous names in different parts of the world and several language specific vernacular names. The herb has been extensively studied as well as reported in several fields of science. The multiple potential of the herb includes allelopathic potential, antibacterial property, antimicrobial activity, insecticidal property; free radical scavenging and radio-protective components from herb extracts and most recently the appetizing potential of the herb have been reported. The herb has carvacrol and thymol as the major components responsible for the flavour; while chlorogenic acid, rosmarinic acid etc. as the phenolic components. The herb has been used in therapeutic and medicinal applications as well as in culinary preparations.

Plectranthus amboinicus (Lour.) Spreng: Botanical, Phytochemical, Pharmacological and Nutritional Significance

Plectranthus amboinicus (Lour.) Spreng. is a perennial herb belonging to the family Lamiaceae which occurs naturally throughout the tropics and warm regions of Africa, Asia and Australia. This herb has therapeutic and nutritional properties attributed to its natural phytochemical compounds which are highly valued in the pharmaceutical industry. Besides, it has horticultural properties due to its aromatic nature and essential oil producing capability. It is widely used in folk medicine to treat conditions like cold, asthma, constipation, headache, cough, fever and skin diseases. The leaves of the plant are often eaten raw or used as flavoring agents, or incorporated as ingredients in the preparation of traditional food. The literature survey revealed the occurrence 76 volatiles and 30 non-volatile compounds belonging to different classes of phytochemicals such as monoterpenoids, diterpenoids, triterpenoids, sesquiterpenoids, phenolics, flavonoids, esters, alcohols and aldehydes. Studies have cited numerous pharmacological properties including antimicrobial, antiinflammatory, antitumor, wound healing, anti-epileptic, larvicidal, antioxidant and analgesic activities. Also, it has been found to be effective against respiratory, cardiovascular, oral, skin, digestive and urinary diseases. Yet, scientific validation of many other traditional uses would be appreciated, mainly to discover and authenticate novel bioactive compounds from this herb. This review article provides comprehensive information on the botany, phytochemistry, pharmacology and nutritional importance of P. amboinicus essential oil and its various solvent extracts. This article allows researchers to further explore the further potential of this multi-utility herb for various biomedical applications.

Effect of subinihibitory and inhibitory concentrations of Plectranthus amboinicus (Lour.) Spreng essential oil on Klebsiella pneumoniae

We evaluated the antimicrobial activity and some mechanisms used by subinhibitory and inhibitory concentrations of the essential oil, obtained from leaves of Plectranthus amboinicus, against a standard strain of Klebsiella pneumoniae and 5 multiresistant clinical isolates of the bacteria. The minimal inhibitory concentration (MIC) and minimal bactericidal concentration (MBC), the rate of kill and the pH sensitivity of the essential oil were determined by microdilution tests performed in 96-well plates. Subinhibitory and inhibitory concentrations of the essential oil were tested in order to check its action on K. pneumoniae membrane permeability, capsule expression, urease activity and cell morphology. The MIC and MBC of the essential oil were 0.09±0.01%. A complete inhibition of the bacterial growth was observed after 2 h of incubation with twice the MIC of the essential oil. A better MIC was found when neutral or alkaline pH broth was used. Alteration in membrane permeability was found by the increase of crystal violet uptake when the bacteria were incubated with twice the MIC levels of the essential oil. The urease activity could be prevented when all the subinhibitory concentrations were tested in comparison to the untreated group (p<0.001). Alteration of the bacterial morphology besides inhibition of the capsule expression was verified by atomic force microscopy, and Anthony's stain method, respectively. Our data allow us to conclude that the essential oil of P. amboinicus can be a good candidate for future research.

Essential Oil of Plectranthus tenuicaulis Leaves from Gabon, Source of (R),(E)-6,7-Epoxyocimene. An Unusual Chemical Composition within the Genus Plectranthus

Water distilled essential oils from leaves of Plectranthus tenuicaulis (Hook. f.) J. K. Morton collected in Gabon were analyzed using GC-FID and GC-MS. The main constituent, unusual within the genus Plectranthus, was isolated and formally identified as being the (+)-( R)-enantiomer of ( E)-6,7-epoxyocimene [( E)-myroxide]. This enantiomer, which represents about 75% of the essential oil, has been previously identified as a pheromone emitted by the male fruit-spotting bug Amblypelta nitida; this insect is responsible of destruction of most fruit crops in tropical and subtropical areas. The potential application of P. tenuicaulis essential oil in crop protection programs is discussed and the atypical chemical profile of the gabonese essential oil is compared with those previously reported in the genus Plectranthus (or Coleus).