Commercial Lawsonia inermis L. dried leaves and processed powder: Phytochemical composition, antioxidant, antibacterial, and allelopathic activities

• Determination of the phytochemicals content of henna dried leaves and processed powder.
• Studied henna extracts have potent antioxidant and antibacterial capacities.
• The extracts exhibit allelopathic activity on wheat and canary grass seeds.
• Henna extracts inhibited seed germination, stems and roots elongation.
• Clove powder added to henna improved its biofunctional properties.

Henna (Lawsonia inermis L.) is a plant used over the world for centuries for its medical and cosmetic virtues. The present work aimed to determine the phytochemical composition, antioxidant, antibacterial activities and phytotoxic potentials of commonly commercialized henna’s dried leaves (HL) and processed powder (HP). The chromatographic method, using reversed-phase high-performance liquid chromatography, with diode array detection (RP-HPLC–DAD) coupled to electrospray ionization–mass spectrometry (ESI–MS), showed that HP and HL contained high polyphenolic content estimated to 31.35 ± 2.05 and 20.22 ± 0.23 mg/g of dray starting material, respectively. Gallic acid (16.23%) and eugenol (13.74%) were the most abundant compounds, whereas, luteolin was the major compound in HL (43.41%). Additionally, HP extract showed the strongest antioxidant potentials as assessed by both DPPH and ABTS functional methods with IC50 = 51.36 ± 1.9 and 78.18 ± 1.47 μg/ml, respectively. Antimicrobial potential evaluated using a range of microorganism strains demonstrated that Bacillus subtilis (ATCC6633) was the most sensitive bacteria to both HL and HP extracts with MBC ≈ 165.8 ± 3.7 μg/ml (HP) and 454.3 ± 42 μg/ml (HL). The extracts allelopathic activity on seed germination, stem and root growth of wheat (Triticum aestivum L.) and canary grass (Phalaris canariensis L.) were also assessed in-vitro. Canary grass was the most sensitive species to HL and HP. Both extracts were effective inhibitors of germination, stem and root growth in a dose-dependent manner. These findings could support the potential applications of HL and HP extracts as natural herbicide. Obtained data reveal that commercial HP contained an additional product that strengthened its chemical and functional properties, particularly, clove (Syzygium aromaticum) which is frequently supplemented for henna’s cosmetic value improvement.

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