Common Names: Snake Bean, Pau Rosa
Species ID: NMP-212 | wfo-0000192568;NCBI_Taxonomy ID: 149635

Kingdom: Plantae

Phylum: Tracheophyta

Class: Magnoliopsida

Order: Fabales

Family: Fabaceae

Genus: Bobgunnia

Species: Bobgunnia madagascariensis

Synonyms: Swartzia madagascariensis Desv., Swartzia marginata Benth., Swartzia sapinii De Wild., Tounatea madagascariensis (Desv.) Baill., Cassia madagascariensis Poir. ex Desv.

Bobgunnia madagascariensis, commonly known as Snake Bean or Pau Rosa, is a semi-deciduous small tree or shrub, typically 3–4 m tall, occasionally reaching 15 m with a bole diameter up to 60 cm. Its key features include:

·       Stem: Stems and branches are often twisted and contorted; bark is dark grey, rough, fissured, and flaking, with a yellowish-white inner bark exuding crimson-black mucilage (Hyde et al., 2015).

·       Leaves: Imparipinnate, alternate, 10–20 cm long, with 5–11 (rarely 13) elliptic to obovate leaflets, 2.5–7 cm long; leaflets are leathery, dark green and glabrous above, yellowish and velvety beneath; petiole 2–4 cm long (Kew Science, 2024).

·       Flowers: Sweetly scented, in lax, 2–10-flowered racemes up to 8 cm long; flowers are bisexual, zygomorphic, with one large white petal, grey-margined, yellow at the base, and numerous orange-yellow stamens (Hyde et al., 2015).

·       Fruits: Cylindrical, indehiscent pods, 15–30 cm long, 2–3 cm wide, dark brown to black when ripe, containing 1–6 flat, brown seeds, 1–2 cm long (Neuwinger, 2004).

·       Seeds: Flat, brown, 1–2 cm long, released when pods rot on the ground; remain viable for years if kept dry and insect-free (Options NRI, 2024).

The tree’s dense, rounded crown and attractive flowers make it a candidate for ornamental use, though its primary value lies in its wood and medicinal properties (Hyde et al., 2015).

Bobgunnia madagascariensis is widely distributed across tropical and southern Africa, from Senegal, Guinea, and Chad in the west to Tanzania, Zambia, and northern South Africa in the east, and south to Namibia, Botswana, and Mozambique. Despite its name, it is not found in Madagascar. It thrives in:

·       Climatic conditions: Semi-arid to humid tropical climates with annual rainfall of 500–1,500 mm and temperatures of 20–30°C (Kew Science, 2024).

·       Altitude: 150–1,750 m, primarily in valleys and humid plains (Options NRI, 2024).

·       Habitats: Deciduous woodlands, wooded grasslands, savannas, and open scrub; often on sandy or clay-loam soils with good drainage (Hyde et al., 2015).

·       Ecological role: Found in disturbed areas and along watercourses, contributing to soil stabilization (Neuwinger, 2004).

In Nigeria, it is common in the northern savanna regions, particularly in Bauchi and Kaduna states, where it grows in wooded grasslands (Schaller et al., 2001).

Bobgunnia madagascariensis is a significant plant in African traditional medicine, particularly in West and Southern Africa, with ethnopharmacological studies supporting its uses:

·       Galactogenic properties: In Benin, decoctions of stem bark and leaves are used by women to promote lactation post-childbirth. Studies in the Sudanian and Sudano-Guinean zones confirm its traditional use as a galactagogue, though specific bioactive compounds remain unidentified (Houndjo et al., 2024).

·       Antifungal activity: Root bark extracts contain quinone methide diterpenes (e.g., swartziadione, swartzianin), exhibiting antifungal activity against Candida albicans and Aspergillus niger (MIC 25–50 µg/mL). These compounds disrupt fungal cell membranes, validating traditional use for skin infections (Schaller et al., 2001).

·       Acaricidal properties: Methanol fruit extracts demonstrate 100% mortality against Amblyomma variegatum ticks within 24 hours (LD50 0.030 w/v), supporting its use in ethnoveterinary medicine for tick control in livestock (Muyobela et al., 2016).

·       Poison fishing and arrow poison: Seeds and stem bark contain saponins and diterpenoids used in Nigeria and Zambia to poison fish for easy capture and by the San people for arrow poisons. These compounds cause paralysis in fish and mammals by disrupting neurological function (Neuwinger, 2004).

·       Anthelmintic potential: In Zimbabwe, stem bark decoctions are used to treat intestinal worms in humans and livestock. Preliminary studies confirm larvicidal activity against Haemonchus contortus, likely due to saponins (Adeyemi & Amupitan, 2010).

Phytochemical analyses reveal saponins, diterpenoids (e.g., swartziadione), flavonoids, and alkaloids as key constituents, contributing to its pharmacological effects. However, clinical trials are lacking, and standardization of dosages is needed (Schaller et al., 2001; Adeyemi & Amupitan, 2010).

⚠  Toxicity Profile: Bobgunnia madagascariensis is highly toxic and requires careful handling: Neurological toxicity: Seeds and stem bark contain saponins and diterpenoids that cause paralysis and respiratory failure in fish and mammals, used in poison fishing and arrow poisons by the San people (Neuwinger, 2004). Potential cytotoxicity: High doses of methanolic extracts may be cytotoxic to mammalian cells, as seen in related Fabaceae species (Adeyemi & Amupitan, 2010). Precautions: Ingestion or improper handling can lead to severe poisoning. Pregnant women, children, and individuals with liver or kidney issues should avoid use. Always consult a healthcare professional (Schaller et al., 2001).

·       Wood: Known as Pau Rosa, the heartwood is pink to reddish-brown with high luster, valued for furniture, carvings, musical instruments, and specialty items due to its durability and workability (The Wood Database, n.d.).

·       Ecological: Used in reforestation and soil stabilization in degraded savanna landscapes due to its adaptability to sandy soils (Options NRI, 2024).

·       Cultural: In Zambia, the bark is used to produce a red dye for textiles, and the wood is crafted into ceremonial objects (Hyde et al., 2015).

·       Pesticidal: Fruit extracts are used in Zimbabwe to control crop pests, leveraging their insect-repellent properties (Muyobela et al., 2016).

Bobgunnia madagascariensis - Wikipedia

Bobgunnia madagascariensis - Options NRI

Bobgunnia madagascariensis - PROTA

Bobgunnia madagascariensis - Plants of the World Online

Bobgunnia madagascariensis - GBIF

• Methyl paraben
• Lup-20(29)-en-3β-ol

Adeyemi, M. H., & Amupitan, J. O. (2011). Chemical and biological evaluation of the stem bark of Bobgunnia madagascariensis (Desv.) JH Kirkbr. & Wiersema). J Basic Appl Chem, 1, 46-51.