Piper regnellii

The most active antimicrobial neolignan of the plant, with strong activity against Staphylococcus aureus including MRSA (MIC ~1-8 µg/mL) and additional antifungal, antileishmanial, trypanocidal and anti-PAF activity.

Highly active against S. aureus (MIC ~1.56 µg/mL) and Bacillus subtilis (MIC ~3.12 µg/mL); contributes to the antibacterial reputation of the leaves.

One of the four characteristic neolignans, sharing antibacterial and antifungal activity of the group.

Active against S. aureus and B. subtilis (MIC ~6.25 µg/mL) and reported to have insecticidal and antifungal properties.

The aromatic leaf oil contributes to antimicrobial activity and to the plant's traditional use as a wound and anti-inflammatory remedy.

In Brazilian folk practice (“caapeba” / “pariparoba”) crushed fresh leaves or roots are applied as a plaster or poultice to wounds, swellings and skin infections, consistent with the antibacterial neolignan content.

An infusion or decoction of the leaves is used externally to bathe wounds and inflamed skin. Human dosing has not been studied; internal use is not well characterised, so external application is the documented traditional route.

Ethyl acetate extract and isolated neolignans were tested against 64 clinical MSSA/MRSA isolates. Eupomatenoid-5 was the most potent (MIC 1-8 µg/mL; MIC50 4 µg/mL against both MSSA and MRSA), supporting the traditional use of the leaves against skin infections.

Neolignans from P. regnellii, notably eupomatenoid-5 and conocarpan, showed activity against Mycobacterium tuberculosis, identifying the dihydrobenzofuran neolignans as leads for antitubercular research.

Known in Brazil as caapeba or pariparoba, the leaves and roots have long been used in domestic medicine as poultices and washes for wounds, swelling and infections; the name pariparoba is also shared with other Piper species used similarly.