## 3 Discovering Polysaccharides in Africa
### A Focus on Bioactive and/or Functional Polysaccharides from Arid and Semi-Arid Lands
#### 3.3.1. Acacia
\begin{table}
\begin{tabular}{c c c c} \hline \hline
**Characteristics** & **General Information** & _A. senegal_ **Gum** & _A. segal_ **Gum** \\ \hline \multirow{2}{*}{Specific rotations} & Differences were described is due to the variation of & Negative specific rotations: & Positive specific rotations: \\  & monosaccharide. _A. segal_ gum contained more Ara than Rha & \(-26\) to \(-34^{\circ}\) [128] & \(+60^{\circ}\) [129] \\  & residues [127] & \(-30^{\circ}\) [127] & \(+54^{\circ}\) [127] \\ \hline \multirow{2}{*}{\begin{tabular}{c} Rheological \\ behavior \\ \end{tabular} } & \multirow{2}{*}{Gums are more described for their emulsifying properties} & Viscous [130] & Low viscosity [130] \\ \cline{2-2}  & & & \(1.14\times 10^{6}\) g mol\({}^{-1}\) for _A. segal_[131] \\ \hline \multirow{2}{*}{Molecular weight} & \multirow{2}{*}{Molecular weights are often higher than 1M Da} & \multirow{2}{*}{\(0.485\times 10^{6}\) g mol\({}^{-1}\) [131]} & \(2.1\times 10^{6}\) for _A. segal_ var. _faillia_[132] \\  & & & \(1.7\times 10^{6}\) for _A. segal_ var. _segal_[133] \\ \hline \multirow{4}{*}{Structural features} & Main chain structures of \(\beta\)-(1,3)-Gal with numerous & \multirow{2}{*}{\begin{tabular}{c} Ara/ Gal ratio \(<\) 1 [126; 130] \\ Higher proportion of rhamnee [130] \\ \end{tabular} } & \multirow{2}{*}{\begin{tabular}{c} Ara/ Gal \(>\) 1 [126; 130] \\ Low rhamne content [130] \\ \end{tabular} } \\  & branching points in O-6 positions of O-Gal residues. Lateral & Hyperbranched structure with degree & \\ \cline{1-1}  & chains have units of \(\alpha\)-L-ra & & \multirow{2}{*}{\
\begin{tabular}{c} Hyephened Caj, shorter Araf \\ ramifications, and more Rha in \\ terminal positions [125; 133] \\ \end{tabular} } & \multirow{2}{*}{
\begin{tabular}{c} Less degree of branching (around \\ 59%) [125; 133] \\ \end{tabular} } \\ \cline{1-1}  & & & & \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Main characteristics of _A. senegal_ and _A. seval_ gums. \begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Acacia Species** & \multicolumn{4}{c}{**Main Monosaccharides (\% Molar Ratio)**} & \multicolumn{2}{c}{**Reference**} \\ \hline \multirow{3}{*}{_A. glomeras_} & Gal & Ara & Rha & GlcA & \\  & 46 & 27 & 15 & - & [116] \\ _A. macraantha_ & 43 & 30 & 5 & 22 & [117] \\ _A. senegal_ & 39–42 & 24–27 & 12–16 & 15–16 & [118] \\ _A. segal_ & 38 & 45 & 4 & 7 & [119] \\ _A. tortilis_ var. _raddiana_ & 19 & 78 & 2 & 4.4 & [120] \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Monosaccharide compositions of polysaccharides extracted from some _Acacia_ species in arid lands. _A. tortilis_ is also called Israeli Babool or umbrella thorn. This species can tolerate drought and stretches extensively over arid and semi-arid regions of Africa, Algeria, Egypt, Israel, Asia and India. The seeds were composed of 14.3% fiber and 45.3% carohyd-drates [134]. [PERSON] indicated that the gum exudates of _A. tortilis_ ssp. _radidana_ (Savi) Brenan consisted of L-Ara, D-Gal, D-Glc, L-Rha and D-Man, with some molar ratios around 78%, 18%, 0.6%, 1.7% and 0.7% respectively [120]. Gas chromatographic analyses also showed the presence of 4% and 4.4% of D-GalA and D-Glc respectively.