Ian Edwin Cock

An examination of the medicinal potential of Scaevola spinescens: Toxicity, antibacterial, and antiviral activities

Background: Scaevola spinescens is an endemic Australian native plant with a history of use as a medicinal agent by indigenous Australians. Yet the medicinal bioactivities of this plant are poorly studied. Materials and Methods: S. spinescens solvent extracts were tested for antimicrobial activity, antiviral activity and toxicity in vitro. Results: All extracts displayed antibacterial activity in the disc diffusion assay. The methanol extract proved to have the broadest specificity, inhibiting the growth of 7 of the 14 bacteria tested (50%). The water, ethyl acetate, chloroform, and hexane extracts inhibited the growth of 6 (42.9%), 5 (35.7%), 5 (35.7%), and 4 (28.6%) of the 14 bacteria tested, respectively. S. spinescens methanolic extracts were equally effective against Gram-positive (50%) and Gram-negative bacteria (50%). All other extracts were more effective at inhibiting the growth of Gram-negative bacteria. All extracts also displayed antiviral activity in the MS2 plaque reduction assay with the methanol, water, ethyl acetate, chloroform, and hexane extracts inhibiting 95.2 ± 1.8%, 72.3 ± 6.3%, 82.6 ± 4.5%, 100 ± 0% and 47.7 ± 12.9% of plaque formation, respectively. All S. spinescens extracts were nontoxic in the Artemia fransiscana bioassay with no significant increase in mortality induced by any extract at 24 and 48 h. The only increase in mortality was seen for the water extract at 72 h, although even this extract displayed low toxicity, inducing only 41.7 ± 23.3% mortality. Conclusions: The lack of toxicity of the S. spinescens extracts and their inhibitory bioactivity against bacteria and viruses validate the Australian Aboriginal usage of S. spinescens and indicates its medicinal potential.

Protective Efficacy of the Antioxidants Vitamin E and Trolox Against Microcystis aeruginosa and Microcystin-LR in Artemia franciscana Nauplii

This study was undertaken to evaluate the protective efficacy of the antioxidants vitamin E and Trolox (a water-soluble vitamin E derivative) against the toxicity of microcystin-LR (MC-LR), Microcystis aeruginosa aqueous extract (CE), and a reference toxin, menadione sodium bisulfite (MSB), in Artemia franciscana nauplii. This was achieved by using the well-established brine shrimp bioassay. The experiment was conducted in 2 stages, with (1) 12-h mortality time course and (2) LC50 determination for 12- and 24-h exposures. Treatments consisted of MC-LR, CE, and MSB alone and with 4-h pretreatments of either vitamin E or Trolox. Sensitivity of A. franciscana nauplii with 24-h LC50 values of 11 (10.1–12.1) μg/ml for MSB and 9.5 (8.8–10.4) μg/ml for MC-LR were in general agreement with values reported for Artemia sp. Both antioxidant pretreatments resulted in significant reductions in mortality of approximately 50% at 9 h postexposure when challenged by either 40 μg/ml MC-LR or 20 μg/ml MSB. In contrast, the antioxidant pretreatments offered little to no protection from CE, suggesting that other uncharacterized bioactive compounds contributed to overall toxicity. The described bioassay is easily accessible, inexpensive, rapid, and complies with animal ethics guidelines of many countries, and thus provides a potential alternative to the mouse bioassay for the initial screening for chemoprotectants against MC-LR toxicity.

Bioactivity of Syzygium jambos methanolic extracts: Antibacterial activity and toxicity.

Methanol extracts from S. jambos leaves were tested for antimicrobial activity and toxicity. S. jambos leaf extract inhibited the growth of 4 of the 14 bacteria tested (29%). Both gram-positive and gram-negative bacterial growths were inhibited by S. jambos leaf extract, although gram-positive bacteria appeared more susceptible. Two of the 10 gram-negative bacteria (20%) and 2 of the 4 gram-positive bacteria (50%) tested had their growths inhibited by the extract. The leaf extract also proved to be toxic in the Artemia franciscana bioassay, with a 48-h LC50 of 387.9 ± 38.8 µg/mL, making it slightly more toxic than Mevinphos (505.3± 37.7 µg/mL) and approximately 5-fold less toxic than potassium dichromate (80.4 ± 4.3 µg/mL). Whilst potassium dichromates LC50 remained constant across the 72-hour test period (24-h LC50, 86.3 ± 5.1; 72-h LC50, 77.9 ± 4.9), the extract and Mevinphos LC50 values decreased by 72 hours (87.0 ± 11.3 µg/mL and 103.9 ± 12.8 µg/mL, respectively), indicating their similar levels of toxicity in the assay.

The medicinal properties and phytochemistry of plants of the genus Terminalia (Combretaceae)

Plants of the genus Terminalia are amongst the most widely used plants for traditional medicinal purposes worldwide. Many species are used for their antibacterial, antifungal, antiprotozoal, antiviral, antidiarrhoeal, analgesic, antimalarial, antioxidant, antiinflammatory and anticancer activities. Wound healing and cardiovascular effects have also been credited to some species. Many Terminalia species have multiple beneficial effects for multiple diseases and ailments. Indeed, the Indian species Terminalia chebula is known as the king of plants in Ayurveda due to its broad range of medicinal uses. However, apart from the reported ethnopharmacological uses of many Terminalia species, surprisingly few studies have rigorously examined this important genus for their medical properties/mechanisms and phytochemistry. This is likely due to the high tannin content common to many Terminalia species and the perception that these tannins may be responsible for much of their beneficial properties. As the complexities of tannins make them poor candidates for drug design, most interest in Terminalia species has been for their pharmacognostic and nutraceutical value and they have often been overlooked as potentials for drug discovery. However, recent reports have identified many other interesting phytochemicals and demonstrated that these may be responsible for several of the reported bioactivities of the Terminalia species used in traditional medicinal systems. The last decade has seen a large increase in the number of studies into the use of Terminalia species as therapeutic agents. Several species used in Ayurvedic medicine (Terminalia arjuna, Terminalia bellerica, Terminalia catappa, T. chebula) in particular have received much recent attention. Similarly, recent reports have also highlighted the medicinal potential of species from Africa, Australia and the Americas. The aim of this report is to summarise the recent research into the medicinal properties, phytochemistry and therapeutic mechanisms of Terminalia species and thus to highlight and direct future areas of research into the medicinal activities of this important genus.

The chemotherapeutic potential of Terminalia ferdinandiana: Phytochemistry and bioactivity

Plants contain a myriad of natural compounds which exhibit important bioactive properties. These compounds may provide alternatives to current medications and afford a significant avenue for new drug discovery. Despite this, little information is available in the literature regarding native Australian plants and their potential for medicinal and industrial uses. Recent studies have reported Terminalia ferdinandiana to be an extremely good source of antioxidants. Indeed, T. ferdinandiana has been reported to have ascorbic acid levels per gram of fruit more than 900 times higher than blueberries. T. ferdinandiana also has high levels of a variety of other antioxidants, including phenolic compounds and anthocyanins. Antioxidants have been associated with the prevention of cancer, cardiovascular diseases, and neurological degenerative disorders. They are also linked with antidiabetic bioactivities and have been associated with the reduction of obesity. Antioxidants can directly scavenge free radicals, protecting cells against oxidative stress-related damage to proteins, lipids, and nucleic acids. Therefore, T. ferdinandiana has potential in the treatment of a variety of diseases and disorders and its potential bioactivities warrant further investigation.

No evidence of antiseptic properties and low toxicity of selected Aloe species

Background and Aim: Closely related plant species often share similar secondary metabolites and bioactivities and are therefore good targets for bioactivity testing when one or more species within a genus are known to possess therapeutic properties. The genus Aloe has a long history of medicinal usage in many areas of the world. Many species are known to have therapeutic properties, several species of which have well-established antibacterial bioactivities. The current studies examine the toxicity of several Aloe species and their ability to inhibit bacterial growth and compare them to the most extensively studied species, Aloe barbadensis, which has well-established antibacterial bioactivities. Results: A. barbadensis methanolic extract displayed broad spectrum antibacterial activity, inhibiting the growth of 8 of the 14 bacteria tested (57%). It was effective against both Gram-positive and Gram-negative bacteria, inhibiting the growth of 4 of 4 Gram-positive bacteria (100%) and 4 of 10 Gram-negative (40%) bacteria tested, respectively. In contrast, Aloe elgonica, Aloe pruinosa, Aloe chabaudii, Aloe daiyana, Aloe marlothi and Aloe vryheidensis all showed no antibacterial activity toward any of the bacteria tested. All of the Aloe species displayed low toxicity similar to that of the A. barbadensis control. A. daiyana was the most toxic of the Aloe species tested with 24, 48 and 72 hours LC50 values of 1018.2, 517.0 and 405.7 ΅g/ml, respectively. Conclusions: Despite their close taxonomic relationship, A. elgonica, A. pruinosa, A. chabaudii, A. daiyana, A. marlothi and A. vryheidensis do not have the same antibacterial medicinal potential as A. barbadensis, but may still have other similar toxicity-related bioactivities. Testing against protozoa, fungi, virus and tumor cells is required to determine if this is the case.

Brine shrimp bioassay: Importance of correct taxonomic identification of Artemia (Anostraca) species

Despite the common use of the brine shrimp bioassay in toxicology, there is confusion in the literature regarding citation of the correct taxonomic identity of the Artemia species used. The genus Artemia, once thought to be represented by a single species Artemia salina, is now known to be composed of several bisexual species as well as parthenogenetic populations. Artemia franciscana is the best studied of the Artemia species and is considered to represent the vast majority of studies in which Artemia is used as an experimental test organism. We found that in studies referring to the use of A. salina, the zoogeography of the cyst harvest site indicated that the species used was actually A. franciscana. Those performing bioassays with Artemia need to exercise diligence in assigning correct species identification, as the identity of the test organism is an important parameter in assuring the validity of the results of the assay.

Invasive character of the brine shrimp Artemia franciscana Kellogg 1906 (Branchiopoda: Anostraca) and its potential impact on Australian inland hypersaline waters.

Brine shrimp (Artemia species) are a major faunal element in many hypersaline biotopes throughout the world and are used extensively in aquaculture, the aquarium trade, solar salt fields and in toxicity bioassays. Commercially available brine shrimp are generally Artemia franciscana cysts, primarily harvested from Great Salt Lake, Utah, USA. The invasive potential of this species raises concerns about its presence in Australia. We reviewed recent overseas reports of the occurrence of A. franciscana populations and confirm that the use of this species has extended its natural geographic range through both deliberate and inadvertent releases. In Australia, Artemia species have been previously identified as being a threat to ecosystem health and biodiversity; however, the specific recognition of A. franciscana was not made. In reviewing the biogeography of Artemia species in Australia, we provide a collation of the reported populations of A. franciscana. The biological attributes of this species contributing to its invasive success are also compiled. The implications of further releases and increases in the range of this species to Australian inland waters are discussed. We appeal for increased vigilance regarding the importation and use of this potentially highly invasive species and monitoring for its presence.

Gas chromatography‑mass spectroscopy analysis of bioactive petalostigma extracts: Toxicity, antibacterial and antiviral activities

Background: Petalostigma pubescens and Petalostigma triloculare were common components of pharmacopeias of multiple Australian Aboriginal tribal groupings which traditionally inhabited the areas in which they grow. Among these groups, they had a myriad of medicinal uses in treating a wide variety of bacterial, fungal and viral infections. This study was undertaken to test P. pubescens and P. triloculare leaf and fruit extracts for the ability to inhibit bacterial and viral growth and thus validate Australian Aboriginal usage of these plants in treating bacterial and fungal diseases. Materials and Methods: P. pubescens, and P. triloculare leaves and fruit were extracted and tested for antimicrobial, antiviral activity and toxicity. The bioactive extracts were further examined by RP-HPLC and GC-MS to identify the component compounds. Results: The methanol, water and ethyl acetate leaf and fruit extracts of displayed potent antibacterial activity. The methanol and ethyl acetate extracts displayed the broadest specificity, inhibiting the growth of 10 of the 14 bacteria tested (71%) for the leaf extract and 9 of the 14 bacteria tested (64%) for the fruit extracts. The water extracts also had broad spectrum antibacterial activity, inhibiting the growth of 8 (57%) and 7 (50%) of the 14 bacteria tested, respectively. All antibacterial extracts were approximately equally effective against Gram-positive and Gram-negative bacteria, inhibiting the growth of 50-75% of the bacteria tested. The methanol, water and ethyl acetate extracts also displayed antiviral activity in the MS2 plaque reduction assay. The methanol and water extracts inhibited 26.6-49.0% and 85.4-97.2% of MS2 plaque formation, respectively, with the fruit extracts being more potent inhibitors. All ethyl acetate extracts inhibited 100% of MS2 plaque formation. All extracts were also non-toxic or of low toxicity. Analysis of these extracts by RP-HPLC showed that the P. triloculare ethyl acetate fruit extract was the least complex of the bioactive extracts. Subsequent analysis of this extract by GC-MS revealed that it contained 9 main compounds: acetic acid; 2,2-dimethoxybutane; 4-methyl-1,3-dioxane; decane; unadecane; 2-furanmethanol; 1,2-benzenediol; 1,2,3-benzenetriol; and benzoic acid. Conclusion: These studies validate Australian Aboriginal therapeutic usage of Petalostigma species and indicate their medicinal potential.

The medicinal potential of Australian native plants from Toohey Forest, Australia

Eleven methanolic extracts of ten Australian native plants from Toohey Forest, Brisbane, Australia wer e investigated for their potential medicinal value as antibacteria l agents. All plants showed some antibacterial acti vity against at least one of the bacteria tested. Alcaligenes faecalis, A eromonas hydrophilia and Bacillus cereus were the m ost susceptible bacteria, being inhibited by 9, 9 and 10 of the pla nt extracts respectively. Davallia pyxidata and Mar chantia polymorpha extracts were least effective, inhibiting the growt h of only 1 or 2 bacteria respectively. Acrotriche aggregata, Petalostigma pubescens, Leptospermum trinervia and Planchonella queenslandica leaf extracts were particularly effec tive bacterial agents being capable of inhibiting the growth of 8 (57%), 10 (71%), 9 (64%) and 9 (64%) of the bacteri a tested respectively. A. aggregata, P. pubescens and L. tri nervia leaf extracts displayed low toxicity in the Artemia franciscana nauplii bioassay, confirming their potential as ant ibacterial agents for medicinal use.