RALAIBIA

Sustainable management of organic residues is a major challenge for modern agriculture. Pyrolysis appears as a promising technology to convert biomass into a stable carbon-rich material called biochar. The aim of this study was to evaluate the potential of pyrolysis residues from whole Malagasy zebu horns (Bos indicus) as an organic amendment to improve soil fertility. Pyrolysis, carried out at controlled temperatures (450–490 °C) in a handmade furnace, resulted in a mass yield of approximately 40 %. The residues showed a high ash content (66.19 %), low moisture (4.09 %), and notable concentrations of major nutrients: total nitrogen 3.59 g/100 g, phosphorus 3.34 g/100 g, and potassium 0.089 g/100 g. Incorporation of these residues into soil could enhance water retention, nutrient availability, and organic matter stability. This study highlights the agronomic and environmental value of valorizing pyrolysis residues within a circular economy approach. Author Keywords: Pyrolysis, biochar, soil fertility, organic amendment, residue valorization, sustainable agriculture.

Objective: In the present study, the essential oil of Athroisma proteiformis was characterized for the first time. Method: GC-HRMS (Gas Chromatography-High Resolution Mass Spectrometry) was performed for qualitative and quantitative analysis of the phytochemicals present in the extract. Chemical analyses were conducted to evaluate the total phenols, total flavonoids and antioxidant activity of the extract. Results: Of the 130 peaks detected, 50 were studied and 30 compounds were clearly identified. The main components of the extract were p-cymen-8-ol, the major compound (13.37%), followed by caryophyllene oxide (12.02%), o-cymene (7.79%), humulene epoxide II (7.62%) and limonene (7.35%). The essential oil of Athroisma proteiformis exhibited a good antioxidant activity. The Athroisma extract IC50 values were lower than those of the antioxidant standards used in the FRAP and ABTS tests, ascorbic acid and BHT, and lower than glutathione in the OH radical reducing power test. On the contrary, in the DPPH test, IC50 was higher for A. proteiformis than for ascorbic acid or BHT. Conclusion: It can be concluded that the A. proteiformis plant can be used as a source of natural antioxidants but the consequences on human health should first be carefully studied due to the large number of compounds present in the oil. Keywords: Antioxidant activity, Asteraceae, Athroisma proteiformis, caryophyllene oxide, essential oil, p-Cymen-8-ol.

The essential oil of the 'resurrection plant' Myrothamnus moschatus (Baillon) Niedenzu endemic to Madagascar, where it is used in traditional medicine, was investigated for the first time for some biological activities. GC-FID and GC-MS analyses revealed trans-pinocarveol (35.6%), pinocarvone (20.0%), β-selinene (8.5%) and perillyl acetate (6.0%) as the major essential oil constituents. The oil strongly inhibited MDA-MB 231 (human breast adenocarcinoma) cells, with an IC(50) of 15 µg mL(-1), and the growth of Candida albicans, with an inhibition diameter of 18 mm, while its antioxidant activity, measured by DPPH and ABTS assay, proved to be negligible.