Many tropical invasive species have allelopathic effects that contribute to their success in native plant communities. Pyrolyzed biomass (“biochar”) can sorb toxic compounds, including allelochemicals produced by invasive plants, potentially reducing their inhibitory effects on native species. Strawberry guava (Psidium cattleianum) is among the most important allelopathic invasive species in tropical islands and recognized as the most serious invasive species threat in the global biodiversity hotspot of Mauritius. We investigated the effects of additions of locally produced biochar on native tree species in a field experiment conducted in areas invaded by strawberry guava within Mauritius’ largest national park. Growth and survivorship of native tree species were monitored over 2 ½ years in plots subjected to four treatments: non-weeded, weeded, weeded + 25 t/ha biochar and weeded + 50 t/ha biochar. Native tree growth and survivorship were strongly suppressed by strawberry guava. Biochar treatments dramatically increased native tree performance, with more than a doubling in growth, and substantially increased native tree survivorship and species diversity, while suppressing strawberry guava regeneration, consistent with growth-promoting properties and sorption of allelochemicals. We conclude that biochars, including “sustainable biochars” produced from locally accessible biomass using low-tech pyrolysis systems, have considerable potential to counteract effects of allelopathic invaders and increase the capacity for native species regeneration in tropical island ecosystems.

Guava (Psidium guajava L.) is a common fruit tree that grows in several tropical and subtropical parts of the world. The aim of this study was to employ the use of liquid-liquid fractionation to investigative the comparative antibacterial potential of crude extracts of Guava leaves and bark against selected food isolates; Escherichia coli, Pseudomonas aeruginosa, Streptococcus pneumonia, Bacillus cereus and Staphylococcus aureus. The phytochemical analysis of the extract showed presence of tannin, phenol, flavonoid and terpenoid in all extract, while steroid and saponin were absent in some. The agar diffusion method was employed for the assessment of the sensitivity of the extracts. The ethyl acetate and aqueous fractions from the stem bark acetone extract generally showed better antimicrobial activity compared with other extracts from leaves. The extract was active both against gram positive bacteria (Bacillus cereus and Streptococcus pneumonia) and gram negative bacteria (Escherichia coli, Pseudomonas aeruginosa, , Bacillus cereus and Staphylococcus aureus) at varying zone of inhibition. The results of the study showed the potential of identifying novel antibacterial agent from P. guajava bark and leaves while optimising the potential application for treatment in traditional medicine.

Over the last decade, Psidium guajava L. (guava) leaves have demonstrated their in vitro and in vivo effect against Diabetes mellitus (DM). However, there is a lack of literature concerning the effect of the individual phenolic compounds present in the leaves in DM disease. For this reason, the aim of the present work was the in silico evaluation of each phenolic compound. The identification of an 80% ethanol extract of guava leaves revealed the presence of 73 compounds. The in silico study carried out with the DIA-DB web server revealed that aldose reductase was the target protein with heterogeneous affinity. Naringenin exhibited the highest number of interactions with target proteins, and compounds like catechin, quercetin, naringenin and morin displayed similarities with known antidiabetic drugs. In conclusion, the computational workflow showed that guava leaves contain several compounds that can play a therapeutic role in the treatment of DM.